Methods and systems for sealing rotating equipment such as expanders or compressors

ABSTRACT

A method and system is provided for pressure balancing one or more seals in machines such as expanders and/or compressors using the process fluid which is being expanded or compressed to provide the pressure for pressure balancing the other side of the one or more seals. The one or more seals may be part of a pressure containing chamber which may comprise a seal, a bearing and/or a gear on a rotating shaft common to the seal. An amount of pressure to be supplied to housing(s) for a machine so as to create a pressure cascade, and thereby dropping the pressure in each subsequent chamber as pressure approaches atmosphere. Pressure differentials may be directed to leak process fluid to the chamber into the process. Pressurized lube oil systems may be employed for balancing pressure and delivering lubricant to the seals, bearings and gears.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Pat. App. No.PCT/CA2014/000435, filed May 20, 2014 to Victor Juchymenko, titled“Methods and Systems for Sealing Rotating Equipment Such as Expanders orCompressors,” which claims priority to U.S. Provisional App. No.61/824,800, titled “Methods and Systems for Sealing Expanders” which wasfiled on May 17, 2013, both of which are incorporated by reference intheir entirety herein.

TECHNICAL FIELD

The present disclosure relates to methods and systems for sealingexpanders and compressors, particularly in industrial applications.

BACKGROUND

Throughout this application, expanders and compressors will be referredto as “machines”. Seal performance limits are typically categorized bythe product of pressure differential across a seal ‘P’ and a sealinterface surface velocity ‘V’, known as the ‘PV’ factor for theapplication. Generally, different seals have differing PV envelopes andlimits. These PV envelopes are both seal-type and application specific.One challenge with successful sealing has been operating within the PVlimit envelope of the seals, or alternately, finding a seal with a PVlimit capacity that is greater than the PV of the particularapplication. The PV limit is an approximation of the conditions to whicha seal will operate, but there may be other factors that influence aseal's capability. Methods for implementing pressure balancingtechniques or pressure differential reduction techniques to mechanicalsealing arrangements to reduce the PV across seals are also known. Forclarity, in this application, pressure balancing or chamber pressuremodification will refer to both a reduction in pressure differentialacross a seal as well as to equalizing pressure across a seal. The belowwill look to describe a unique combination of pressure balancing sealsand pressure cascading approaches to these principles. Use of lip seals,labyrinth seals, mechanical face seals or dry gas seals within expandersand compressors are necessary in “dry” expanders and compressors to keeplubricant separate from process, and are common in rotating equipment.

In addition to PV limits, heat removal from the seal is a criticalcomponent to a sealing solution. Often, lubricant that is used tolubricate bearings, gears and other rotating equipment is alsocirculated onto the seal to assist with lubrication and to remove heatfrom the seal. That lubricant is then typically externally cooled in aheat exchanger and recirculated back into the rotating equipment.Typically, lubricant circulation systems are vented to atmosphere and donot operate as a pressurized system, under a pressure blanket as will bedescribed below.

In many instances, different types of mechanical shaft seals canaccomplish the same PV objective, but may provide other differentadvantages. Throughout this application, mechanical seals, including butnot limited to lip seals, mechanical face seals, dry gas seals, andlabyrinth seals, will be referred to as “seals”. Generally, lip sealshave a lower PV than mechanical seals and are typically better suitedfor higher speeds (higher V) and lower pressure differentials (lower P)whereas mechanical face seals are typically better suited for lowerspeeds (lower V) and higher pressure differentials (higher P), althougheach seal type has its limits whether that be with pressure differentialor seal interface speeds. Dry gas seals, also known as non-contacting ordry-running seals, are best suited for sealing gases at high speeds withhigh pressure differentials where sealing of a vapor is required. Drygas seals are non-contacting, dry-running mechanical face seals.Labyrinth seals are another (non-contacting) mechanical seal thatutilize the principle of providing a difficult and obstructive path forthe gas or fluid being sealed. Each step in a labyrinth seal createseddies which then retard the flow from the pressure differential acrossthe seal. These seals are particularly useful in rotating equipmenthaving high rotational speeds, because they are non-contacting andtherefore do not have much, if any, friction.

Methods for implementing magnetic couplings are common in pumps and havebeen described in scroll compressor applications, typically used inrefrigeration systems. Although magnetic coupling use with pumps wereinitially developed to hermetically seal the pump and the contents ofthe pump from the drive mechanism, often not to contaminate the productin the pump, the basic principles of isolating the drive from the pumpcan also be utilized with an expander or compressor to contain vaporfrom escaping. An example of a magnetic coupling used on an expanderwould be in a pressure let down expander or from an expander in use withan organic Rankine cycle (ORC) system. In an ORC system, a dry expanderwould require a lubricating pump to circulate lubricant to the expandersbearings, gears and seals. In the system described below, a processfluid pressure blanket is applied to the lubricant circulation system,and the use of magnetic couplings on the lubricant circulation systempump(s) provides an advantage of not developing leaks to the processthrough the lubricant circulation system, specifically through the sealson the lubricant pumps.

Shaft seals are typically not required on oil-injected (aka oil-flooded)screw expanders or screw compressors, since the bearings and rotors arelubricated by either delivering lubricant to the bearings, from where itflows to the rotors and then to the exit from the machine, or by mixingthe lubricant directly into the process fluid, which then circulateslubricant with the process fluid and lubricates the bearings and rotorsas it passes through the machine. The lubricant is then eithercirculated throughout the system continuously (such as in refrigerationsystems), or the lubricant is separated from the process fluid on exitfrom the rotating equipment machine in a coalescor/separator/misteliminator (as is done in some natural gas compression applications).Once separated, the lubricant is then re-injected into the bearings androtors to flow through the expander or compressor. In situations wherethe process fluid is to remain clean of lubricant contamination, a dryscrew machine is a good option because the lubricant is kept separatefrom the process fluid by mechanical seals. Although a coalescor on anoil-flooded machine may be able to remove almost all of the lubricant,trace amount will remain in the process stream and therefore cancontaminate or build up over time in a closed loop process.Contamination is undesirable in processes such as compressing breathingair or in gas separation processes that require a purity to the productbeing compressed. In pressure let down applications, the pipelinecompany would find it undesirable to end up with lubricant in theirpipeline system and in ORC systems, a build-up can occur and a film oflubricant may develop on the heat exchangers. This lubricant would thenreduce the thermal conductivity of the heat exchangers and reduce theoverall efficiency of the ORC system. Although refrigeration systemsoperate almost exclusively with oil-flooded machines, an opportunity mayexist to use a dry compressor in refrigeration application. Therefore,an option for a dry expander and compressor has its applications.

Should the machine require a gear box, such that the final drive shafthas a different speed from the machine's rotor shaft, then an integralgear box can demonstrate advantages to an external gear box by applyingpressure balancing that will be described below. With an integral gearbox, the sealing of the final drive shaft could be sealed with one ormore seals in a dynamic sealing arrangement that can wear over time andthereby allow ambient air to make its way into the machine housing orallow working vapor out of the machine to atmosphere. A doublemechanical seal is extremely well suited for sealing a final driveshaft. The double mechanical seal can be arranged face-to-face orback-to-back (it is also known as a dual pressurized and dualunpressurized mechanical seal, depending on whether the space in betweenthe two seals is pressurized or not). Throughout this application, adouble mechanical seal, whether pressurized or not will be referred toas a “double seal”. The advantages of a double seal is that it providestwo layers of protection from leaking the system charge to atmosphere aswell as provide a visual indication to an operator when the outer sealhas started leaking. When the inner seals on a pressurized double sealthat is using the systems lubricant to pressurize the double sealscavity leaks, fluid level in the chamber will rise above its normallevel thereby indicating the seal is leaking. Should the outer sealleak, it will become visible to an operator and the seal will garner therequired attention. Should the machine require an integral gear box,such that the final drive shaft has a different speed from the machinesrotor shaft, then a combination of seals, double seals, or a magneticcoupling can be affixed to either the rotor shaft of the machine or thefinal drive shaft of the integral gear box appended to theexpanders/compressors shafts. Similarly, should an integral gear box notbe required, the seals, double seals or magnetic coupling can be affixedto the rotor shaft or the machine.

Another solution to prevent loss of process fluid could be theintegration of a magnetic coupling to the output shaft. This arrangementis desirable as it: 1) preserves the process fluid thereby saving money,2) prevents air from entering the machine housing and thereby preventingcontamination of the process fluid, and 3) makes the system inherentlysafe by preventing leaks of potentially hazardous, flammable orexplosive process fluids. Magnetic coupling technology has notheoretical size limit but there is a size limit to commerciallyavailable magnetic couplings, and therefore the size of machine thatbecomes coupled with a magnetic coupling is limited in size. Further,magnetic couplings for a fixed physical size have a torque limit beforethey start slipping and therefore, higher speed with lower torque outputshafts can extend the range of a particular size of magnetic coupling,rather than lower speed, higher torque shafts.

A magnetic coupling could also be utilized on the lubricant pump(s) sothat the pump(s) can operate at pressures higher than the balancingprocess fluid vapor. The pump(s) will require the capability ofoperating with a positive head pressure from the balancing process fluidvapor, in addition to adding a pressure differential to the lubricant sothat it will flow to lubricate the various components in the system. Toovercome this challenge, replacing pump seals with a magnetic couplingallows the machines lubricant circulation system to operate at higherthan normal pressures while at the same time eliminating the risk of aleak point.

Ambient air can make its way into the expander when the pressure on themachine side of a seal is less than atmospheric pressure. This conditioncan materialize when: 1) the process fluid cools to create a negativepressure and therefore placing the machine chamber in vacuum, drawingambient air into the equipment, or 2) when the machine undergoes a rapidslow down due to a change in high pressure throttle valve position,negative pressure can be effected on the shafts seals thereby allowingambient air to make its way past the seals into the process fluid. Inclosed loop systems such as refrigeration systems and organic Rankinecycle systems, entry of ambient air into the system pollutes the processfluid and reduces the systems efficiency due to non-condensablesentering the sealed system. For any type of seal to be effective, it hasto leak a nominal amount. These nominal amounts are designed to beminimal.

Another suitable approach to sealing lubricant from the process, andsealing the process from atmosphere, is to design the seals to leak. Thedirection of leaking can be designed into the system such that theprocess leaks from the process to the direction of atmosphere. Theprocess fluid that does get past the seal and into the lubricantcirculation system can then be separated from the lubricant andcirculated back into the process at a lower pressure point in thesystem, and the lubricant drained back into the lubricant circulationsystem. Although some efficiency is lost by allowing the process fluidto bleed through the seals and around the machines internal components,it is an effective approach.

U.S. Pat. No. 4,328,684 describes a method for using a magnetic couplingbetween a twin screw compressor and a twin screw expander for use in arefrigeration system. A wall between the compressor housing and theexpander housing contains a magnetic drive that is connected to rotatewith the output shaft of the compressor and input shaft of one of theexpander rotors so that power can be transferred between the two. USPublication number: US 2011/0176948 describes a scroll expander coupledwith a magnetic coupling. However, the configurations described thereinhave numerous drawbacks, and a need therefore exists in the art to findexpander sealing solutions that can handle high operational PV ratiosand provide inexpensive sealing arrangements in a number of differentapplications.

The techniques described herein may apply to any number of processesincorporating expanders, including but not limited to Organic RankineCycle (ORC) processes, and gas pipeline or steam pressure letdownapplications. In the case of compressors, including but not limited torefrigeration, natural gas compression, and air compressor applications.Advantageously, the present techniques may be applied to ORC processesand pressure let down expander applications. More advantageously, thedisclosed techniques may be applied to ORC processes. Even moreadvantageously, the disclosed techniques may be applied to ORCrecovering waste heat and/or ORC systems utilizing one or more twinscrew expanders. It is also possible, as in the case of a condensingexpander, that the processes fluid leaving the expander or the last of aseries of expanders may be either a semi-saturated vapor or a liquid.

SUMMARY

For the purposes of simplicity, the term “machine” as used hereinthroughout this description, and may refer to an expander and/orcompressor (whether turbo, screw, scroll, or other suitableconfiguration). It should be understood by a person of skill in the artthat the methods and systems of the present disclosure are equallyapplicable to both expanders and compressors and that such embodimentare encompassed by the scope of the present disclosure.

The machines disclosed herein can be any type of expander or compressorknown in the art, including, but not limited to single screw, twin screwexpanders, turbo and scroll expanders, or compressors. The techniquesdisclosed herein are advantageously suited to rotating equipmentmachines that use bearings requiring lubricant, although they could alsobe applied to non-lubricated, oil-less, applications where sealing isdesired. In the previous case, the seals typically separate thebearings, lubricated by lubricant, from the process fluid vapor.

The techniques disclosed herein also apply to machines with and withouta speed altering transmission or gear box, and may also apply to sealsfound in expanders or compressors. The types of seals to which thepresent disclosure can apply are not limited and can include: lip seals,labyrinth seals, mechanical face seals or dry gas seals. The machines ofthe present disclosure may or may not have a gear box attached at aninput or output shaft end, as the case may be. The shaft horse powerthat is produced by an expander can be used for power generation amongstother uses such as driving a pump, a fan or a compressor. If the machinewere to be operated as an expander where pressurized process fluid waspiped into the expander machine such that the internal components rotatedue to a pressure drop experienced through the machine, thereby turningthe shaft, and the machine was then to be operated in the oppositedirection by turning the shaft of the machine to create pressuredifferential, that machine would then be operating as a compressor.

The machines, and more advantageously twin screw machines, related tothe present disclosure can have any number of configurations. They mayinclude magnetic couplings, gear boxes, transmissions, combination ofseal types, pressure balancing systems, pressurized lubricantcirculation systems, condensing and non-condensing expanders or thesystems may incorporate multiple machines in parallel or in series.

As will be appreciated in the disclosure below, multiple embodiments aredisclosed for pressure balancing and pressure cascading using processfluid, directional flushing of seals, load shifting (utilizingsequential pressure chambers), speed reduction of output shaft,pressurized lubricant circulation systems, pressure cascade to drivelubricant to lower pressure chambers, pressure cascading to reduce loadon seals, sealing of output shafts, heating vs. cooling of lubricant andassociated control modules.

BRIEF DESCRIPTION OF THE FIGURES

The present disclosure will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, do not limit thepresent disclosure, and wherein:

FIG. 1A, in conjunction with FIGS. 1B-1F, together illustrate variousembodiments of pressure balancing and cascading using process fluid,where FIG. 1A illustrates one embodiment of an expander/compressor withno use of chambers for pressure balancing or pressure cascading fromprocess;

FIG. 1B illustrates an embodiment utilizing the configuration of FIG. 1Atogether, with single chamber on either end of the machine, with thehigh-pressure (HP) chamber sealed from atmosphere, and no pressurebalancing or pressure cascading;

FIG. 1C illustrates an embodiment utilizing the configuration of FIG. 1Atogether with single HP and single low-pressure (LP) chamber ends sealedfrom atmosphere, with no pressure balancing or cascading but PV loadshifting on LP end with two seals;

FIG. 1D illustrates another embodiment showing pressure balancing linesfrom the process into the machines HP and LP gear chambers;

FIG. 1E illustrates another embodiment utilizing the configuration ofFIG. 1D with the addition of separators to separate lubricant from theprocess fluid;

FIG. 1F illustrates another embodiment showing valves and a pressureregulator to reduce pressure between process tap and gear chamber;

FIG. 2A illustrates an exemplary embodiment for directional flushing ofseals utilizing an expander/generator arrangement to allow seals toleak, where an exemplary process is to leak past the seals into thechambers, then tie in the chambers to a lower pressure point in theprocess so as to return the process fluid to the process and thelubricant to the lubricant circulation system;

FIG. 3A, in conjunction with FIGS. 3B-3J, together illustrate variousembodiments of PV-load shifting (sequential cascading pressurechambers), where FIG. 3A illustrates the configuration of utilizing adouble seal on an output shaft;

FIG. 3B, illustrates an exemplary embodiment having an integral gear boxvented to atmosphere with a single chamber on both HP and LP end, withno pressure balancing, and no PV load sharing;

FIG. 3C, illustrates an exemplary embodiment having an integral gear boxwith a single chamber on both HP and LP end, and no pressure balancing,but with PV load shifting over two seals on LP end;

FIG. 3D illustrates an exemplary embodiment having an integral gear boxwith single chamber on both HP and LP end, with no pressure balancingand no PV load shifting as low pressure end is open to atmosphere;

FIG. 3E illustrates an exemplary embodiment having three chambers (oneHP and two LP chambers), with no pressure balancing and therefore no PVload shifting over the seals on LP end, with a last chamber open toatmosphere;

FIG. 3F illustrates an exemplary embodiment having the configuration ofFIG. 3E with PV load shifting set up to operate over three seals on a LPend;

FIG. 3G illustrates an exemplary embodiment having the configuration ofFIG. 3F with pressure balancing (similar to FIG. 1D) and utilizing asystems pressure to PV load shift over the seal in the LP end chamber;

FIG. 3H illustrates an exemplary embodiment having the configuration ofFIG. 3F in a system utilizing pressure balancing for each of the threechambers, and demonstrates PV load shifting, pressure cascade andpressure balancing;

FIG. 3I illustrates an exemplary embodiment having two machines inseries comprising pressure balancing with check valves, wherein if themachines were viewed as expanders, the discharge from the first higherpressure machine becomes the inlet pressure to the second lower pressuremachine, therefore the overall pressure drop from initial inlet toatmosphere is spread over multiple machines (each with multiple sealsand pressure chambers to drop the pressure over);

FIG. 3J illustrates an exemplary embodiment having the configuration ofFIG. 3I comprising pressure regulators, valves, a common drive gear witha rearranged pressure drop from inlet to final discharge over multiplemachines in series, where common pressure is utilized from a finalchamber to the first and second machine;

FIG. 4A, in conjunction with FIGS. 4B-4F, provide various embodiments ofpressurized lubricant circulation systems, where FIG. 4A illustrates anexemplary embodiment comprising a machine with splash lubricationwithout a lubricating pump and incorporates pressure balancingtechniques and PV load shifting on the LP end;

FIG. 4B, illustrates an exemplary embodiment having a single lubricantcirculation system with a single pump, where the lubricant pumpadvantageously pumps higher pressure than the pressure in HP chamber tohave lubricant flow, wherein lubricant is injected into the HP chamberto lubricate the bearings, gears and seal, and then drains to the bottomof the HP chamber, and system pressure in the HP chamber pusheslubricant to LP chamber bearings/seals, and wherein lubricant thendrains back to the pump;

FIG. 4C illustrates an exemplary embodiment comprising a singlelubricant circulation system feeding lubricant to both the high pressureend similar to FIG. 4B and then with pressure cascading the lubricant ispushed into the first low pressure end of the machine, and thensubsequently the lubricant is pushed into the lowest pressure chamber,where pressure balancing is achieved on 3 chambers and the lubricant ispushed by a single pump to all chambers;

FIG. 4D illustrates an exemplary embodiment comprising two lubricantcirculation systems configured to have one for HP chamber pressure, anda second for LP chamber pressure, where pressure balancing is applied toeach chamber from the process, where each pump operates at a pressurehigher than the chamber pressure into which it pumps lubricant;

FIG. 4E illustrates an exemplary embodiment having the configuration ofFIG. 3I with the addition of a single lubricant circulation system,wherein lubricant pressure is commensurate with pressure balancingpressures, and wherein both pressure and lubricant cascade down, workingthrough the system, wherein the lubricant temperature is inverselycorrelated to pressure such that, as the lubricant works its way throughthe process, its temperature will rise;

FIG. 4F illustrates an exemplary embodiment having the configuration ofFIG. 3J and comprising a single lubricant circulation system functioningsimilarly to the lubricant circulation system described in FIG. 4E;

FIG. 5A, in conjunction with FIGS. 5B-5E illustrate various embodimentsof drive shaft sealing techniques, where FIG. 5A is one embodimentshowing LP lubricant system injection into a double seal on the finaldrive shaft, along with a combination of multiple integrations;

FIG. 5B illustrates an exemplary embodiment having the configuration ofFIG. 5A with HP lubricant system injection into double seal on the finaldrive shaft, in place of the lower pressure lubricant circulationsystem, along with a combination of multiple integrations;

FIG. 5C illustrates an exemplary embodiment comprising magnetic couplingon a machine rotor shaft;

FIG. 5D illustrates an exemplary embodiment comprising magnetic couplingon a twin screw machine rotor shaft;

FIG. 5E illustrates an exemplary embodiment comprising magnetic couplingon the final drive shaft of the integrated gear box of theexpander/compressor; and

FIG. 6 illustrates an exemplary embodiment comprising a control modulefor monitoring: temperature, pressure and flow of lubricant and processfluid in the chambers, and for controlling: pump(s), pressure in thechambers, and flow to heat exchanger(s) (air or liquid) for eitherheating or cooling the lubricant.

DETAILED DESCRIPTION

The figures and descriptions provided herein may have been simplified toillustrate aspects that are relevant for a clear understanding of theherein described devices, systems, and methods, while eliminating, forthe purpose of clarity, other aspects that may be found in typicaldevices, systems, and methods. Those of ordinary skill may recognizethat other elements and/or operations may be desirable and/or necessaryto implement the devices, systems, and methods described herein. Becausesuch elements and operations are well known in the art, and because theydo not facilitate a better understanding of the present disclosure, adiscussion of such elements and operations may not be provided herein.However, the present disclosure is deemed to inherently include all suchelements, variations, and modifications to the described aspects thatwould be known to those of ordinary skill in the art.

Some rotating equipment operating pressures are restricted by thatequipments internal seals ability to contain the pressure at thatequipments pressure differential and rotating speed. Provided that therotating equipments housings are capable of containing pressure requiredin the equipment and associated chambers, pressure balancing along withload shifting across multiple seals, along with integral pressurecontaining gear reduction, the pressure capacity of that same equipmentcould be broadened. Many housings are not designed to contain pressurein the gear or bearing chambers, or higher pressures in the mainhousings, but with modified housings and chambers (by use of thickercastings or stronger materials), and with lubricant circulation systemmodifications, equipment that is pressure limited due to the limitationsof the seals, could operate at a higher pressure, and thereby increasethe duty from that same equipment.

Pressure Balancing and Cascading Using Process Fluid

As used herein, the term process fluid 56 may refer to a propellant,also known as vapor, gas, charge, fluid or other energetic materialstravelling through a machine. With reference to any one of FIGS. 1F, 2A,3G, 3H, 4A, 4B, 4C, 4D, and 6, where an ORC system is depicted with anexpander, the process fluid 56 may be in the form of a liquid as itleaves the condenser 55 and through process fluid pump 75. In passingfrom the pump as a liquid and into the ORC heat exchanger 65, theprocess fluid 56 may be evaporated in the ORC heat exchanger 65 to avapor and enters the machine 21 via high pressure process pipe 60 as avapor.

As is illustrated in FIGS. 1D-1F, multiple embodiments are provided,illustrating pressure balancing and pressure cascading using processfluid. As mentioned above, the present disclosure relates to methodsutilizing the pressure of the vapor which is intended to be contained onthe process side of a seal to balance the other side of the seal withthat process fluid. Although the above describes an ORC system forproducing process fluid in vapor form, if the machine were operated inthe opposite direction as a compressor, then the pressure balancingprocess fluid source would be from the compression process. Theprinciple is referred to herein as “pressure balancing” the seal. Mostpressure balancing techniques employ inert gases as the pressurebalancing medium. The embodiments described herein allows pressurebalancing without necessarily introducing additional fluids or gases,other than the process fluid 56 and the lubricant 29 from the system.

In one exemplary embodiment, the pressure differential may be reducedacross high pressure seals 17 and low pressure seals 27, 28 a, 28 b or28 c, if applicable, in the machine 21 by using the existing pressurefrom process fluid 56, which then would reduce the PV factor on theseals by reducing the pressure differential component across some sealsand redistributing the PV factor onto other individual or multipleseals. One method of reducing the PV across a seal, by reducing thepressure differential across a seal, is to divide the overall pressureload between more than one seal or by shifting the load from a singularseal to multiple seals. This can be accomplished by pressurizing thechambers 39 on the high pressure end of the machine 21 or on the lowpressure end 26 a or 26 b, if applicable, on the low pressure end of themachine 21. Another method is to utilize pressure in the process fluid56 to pressurize one or more chambers 26 and 39 and thereby reducing thepressure differentials across high pressure seals 17, and low pressureseals 27, 28 a, 28 b and 28 c, if applicable. The process fluid 56pressure from either the high pressure process pipe 60, the low pressureprocess pipe 70, or other parts of the process can be utilized via apressure balancing line(s) to alter the pressure in the chambers oneither end of the machine. The number and arrangement of chambers 26 and39 on either end of the machine can be structured to effect loadshifting between the seals.

In the FIGS. 1D-1J, 4A-4F, 5B, and 6, pressure balancing to chamber 39is provided by high pressure balancing line 63 connecting chamber 39 tohigh pressure process pipe 60. Because it is desirable to equalize orcascade the pressure downwards in the pressure chambers to haveeffective leaking of the seals, the pressurization of chamber 39 can bepressurized from a lower pressure point in the machine or the process.For example, chamber 39 can be pressurized directly by, or indirectlythrough another component of the machine or process, such as by lowpressure process pipe 70, or process piping between low pressure processpipe 70 and the pump 75. Note, the larger the pressure differentialacross seal 17 is, the larger the PV is on seal 17. Also, chamber 39 canbe pressurized by line 63 with a pressure regulator to reduce thepressure in chamber 39 should it be desirable to be lower than theprocess to facilitate flow away from the process towards atmosphere.Similarly, chambers 26 a, or 26 b can be pressurized by any processfluid source in the machine or the process, whether higher, lower orequal pressure, provided that a high pressure source is regulated downto be less than or equal to the pressure in the process or chamber thatis “upstream” of the current chamber being pressurized, such that thepressure is equal or it continues to drop to cascade toward atmosphere,which is referred to herein as “cascading.”

FIG. 1A provides an exemplary embodiment illustrating a machine 21 withthe chambers 39 on the high pressure end is open to atmosphere 44 andchamber 26 a on the low pressure end is also open to atmosphere 44. Theconcept of pressure balancing does not apply to this configurationbecause the chambers 26 a, 39 are not capable of containing any pressure(as they are open to atmosphere 44). Because pressure cannot becontained in the chambers, cascading with pressure cannot be applied.FIG. 1B shows machine 21 as in FIG. 1A, but where the high pressurechamber 39 is closed to atmosphere 44 and is capable of containingpressure. Thereby, in this configuration, chamber 39 is suitable forapplication of pressure balancing described herein, where chamber 26 ais not because it is vented to atmosphere. FIG. 1C shows the samemachine 21 as FIG. 1B with the low pressure end being sealed, such thatboth the high pressure chamber 39 and the low pressure chamber 26 a arecapable of containing pressure and thereby pressure balancing can beapplied with the addition of pressure balancing lines, and load shiftingof the seals on the low pressure end of the machine can be applied. Asshown in FIG. 1D, process fluid 56 entering the machine 21 through highpressure process pipe 60 and exits the machine 21 through the lowpressure process pipe 70 at a lower pressure than it entered themachine. The pressure drop will be developed as the rotating element 20is rotated by the pressure differential, where the pressure at the highpressure process pipe 60 is greater than pressure at the low pressureprocess pipe 70.

The rotating element 20 is coupled to, and may rotate in unison with,the rotor shaft 14. Each machine may have its own propulsion device, forexample, in a screw machine (single or double), the rotating elementwould be a helical screw component, in a turbo machine, the rotatingelement would be the turbine blades, and in a scroll machine it would bethe scrolls. Supporting the rotor shaft 14 are bearings 16 on the highpressure side of the rotating element 20 and bearings 66 on the lowpressure side of the rotating element 20. As shown in FIG. 3B, betweenthe respective bearings 16 and 66 is the rotating element 20, and oneither side of the rotating element 20 are the high pressure seals 17and the low pressure seals 28 a and 28 b. Between bearing 16 and therotating element 20 is seal 17 on the high pressure side. Betweenbearing 66 and the rotating element 20 is seal 28 a on the low pressureside. The diagrams presented refer to all seals on the low pressure endof the machine 21 by the number 28, then further depicted with a vowelindicating the series the seal is in. As example, 28 a refers to theseal nearest to the rotating element 20, followed by the second-nearestas 28 b, etc.

The high pressure end of the machine 21 may have a high pressure chamber39 which will contain lubricant 29. The low pressure end of the machine21 will have a low pressure chamber 26 a, and in multi-chamberapplications, 26 a and 26 b. Similar to the low pressure seals 28 on thelow pressure end, the chambers 26 on that end will be depicted with aletter indicating the chambers sequential distance from the rotatingelement 20. As an example, if the low pressure end of the machine 21 hastwo chambers 26, the chamber nearest to the rotating element 20 will bereferred to as low pressure chamber 26 a, and the chamber further awayfrom the rotating element 20 will be referred to as low pressure chamber26 b. Should another chamber be appended to the low pressure end of themachine 21, it would be referred to as chamber 26 c. The above assumesthat the drive shaft 24 is on the low pressure end of the machine 21.Should the drive shaft 24 be on the high pressure end of the machine 21,the load shifting concept will be employed on the high pressure end ofthe machine 21, such that the chambers would be labeled 39 a, 39 b, etc.and the seals would be labeled 17 a, 17 b, 17 c, etc.

As shown in the exemplary embodiment in FIG. 1D, the machine 21 maycomprise an integrated gear mechanism 22 contained within chamber 26 a.In an expander configuration, the rotor shaft 14 turns a drive gearwhich then turns another gear that provides resulting shaft power out ofthe output drive shaft 24. The output drive shaft 24 is supported bybearings 88 on both sides of the integrated gear mechanism 22. The rotorshaft 14 has seals 28 a and 28 b designed to contain the lubricant 29and process fluid 56 within low pressure chamber 26 a. The output driveshaft 24 has seal 28 b and seal 28 c designed to contain the lubricant29 and process fluid 56 within low pressure chamber 26 b. In acompressor configuration, the drive shaft 24 would be turned and thegear(s) of the integrated gear mechanism 22 which would then turn therotor shaft 14. As shown in FIG. 1D, the high pressure chambers 39 maybe connected to the high pressure process pipes 60 by pressure balancinglines 63, and the low pressure chambers 26 is connected to the lowpressure process pipes 70 by pressure balancing lines 72. Pressurebalancing line 63 will allow process fluid 56 to pass to and from thehigh pressure process pipe 60 into the high pressure chamber 39.Similarly, a pressure balancing line 72 will allow process fluid 56 topass to and from the low pressure process pipe 70 to the low pressurechamber 26 a. In the case where a separator is utilized between theprocess piping and the chambers, the separator is designed to removelubricant 29 from the process fluid 56 that passes through the pressurebalancing lines. Lubricant recovered by the separator 77 will be drainedby to the respective chamber and the process fluid will flow from higherpressure to lower pressure. A resulting effect on the high and lowpressure seals 17 and 28 a, and 28 b is that the reduced pressuredifferential across the high pressure seals 17 and low pressure seals 28a and 28 b, or seals 28 a and 27, if application of a double seal isselected, results in a lower PV than if the pressure balancing and thuspressure cascading and PV load shifting techniques were not applied.

As shown in the example of FIG. 1E, pressure balancing lines 63 and 72allows flow of process fluid 56 from the high and low pressure processpipes 60 and 70 to the high and low pressure chambers 39 and 26 a,respectively, to facilitate pressure balancing. In this configuration,any process fluid 56 in pressure balancing lines 63, 72 passes through aseparator 77, also known as a coalescor or mist eliminator, beforedraining back to the respective high or low pressure chambers 39, 26 a.The separator 77 is designed to prevent lubricant 29 from entering thehigh and low pressure process pipes 60, 70 and to drain back to the highand low pressure chambers 39, 26 a, while still allowing the flow ofprocess fluid 56 to and from the high and low process pipes 60, 70. FIG.1F shows a variation on pressure balancing lines 63 and 72 shown in FIG.1E. In FIG. 1F pressure balancing line 63 is tied into the high pressureprocess pipe 60 and connects to high pressure chamber 39 through a valve38, and pressure balancing line 62 in this configuration is connected tohigh pressure process pipe 60 through a valve 38 and a pressureregulator 36.

The high pressure end of the rotating element 20 is at or near thepressure at the high pressure process piping 60 on the high pressure endof the machine 21. The high pressure seal 17 is typically located inchamber 39 between the high pressure bearing 16 and the high pressurechamber end of the machine 21. On the other end of the rotor shaft 14,at the low pressure end of the machine 21, there is also, typically, alow pressure seal(s) 28 located between the rotating element 20, and thelubricant 29 used to lubricate low pressure bearing(s) 66. The lowpressure chamber 26 a is utilized to reduce the PV on the low pressureseal(s) 28 a. Low pressure seal(s) 28 b may be located between the lowpressure chamber 26 a and atmosphere 44 or, in cases with multiplepressure reducing chambers, between chamber 26 a and lower pressurechamber 26 b. The rotor shaft 14 typically refers to the higher speedshaft directly coupled to the rotating element 20, whereas the driveshaft 24 typically refers to the lower speed shaft coupled to the rotorshaft 14 by an integrated gear mechanism 22 or other power transmissiondevice. The machine 21 may have an integrated gear mechanism 22 that isstraddled by low speed low pressure bearings 88 and that turns the driveshaft 24. The low pressure chamber 26 a may be sealed from theatmosphere 44 by low pressure seals 28 b, or open to atmosphere 44 by avent. The lubricant 29 serves to lubricate the moving (rotating)components and to remove heat from the bearings, gears and high and lowpressure seals 17, 27, 28. High and/or low pressure seals 17, 27, 28 inany of these configurations can benefit from the present disclosure.

FIG. 1F illustrates an exemplary embodiment applied to an organicRankine cycle (ORC) process. It also shows that the balancing pressurecan come from various points in the process and do not necessarily haveto come from the exact pressure on the other side of the seal. The otherconcept shown in the figure is that pressure can be taken from ahigher-pressure point in the process and its pressure be reduced througha regulator 36. The setting of the regulator 36 will be set to be nearthe pressure of the low pressure process piping 70 so that the pressuredifferential across low pressure seal 28 a is reduced and the resultingPV of the low pressure seal 28 a reduced. If a higher pressure exists inlow pressure chamber 26 a than in the low pressure process pipe 70, thenthe low pressure seal 28 a would tend to leak from the low pressurechamber 26 a into the low pressure process piping 70. This is anundesirable direction of leakage as leakage is preferred in the otherdirection—from the low pressure process pipe 70 pressure (the process)to the low pressure chamber(s) 26. Regardless of leak direction, theconcept of pressure balancing does reduce the load on the seals. As thepressure differential across a seal increases, so does the PV andtherefore wear on the seal also increases, which is inverselyproportional to the life expectancy of the seal.

This structure shows the benefit of the pressure balancing method shownin FIGS. 1D and 1E where the pressure in the high and low pressurechambers 39, 26 a changes with the pressure in the high and low pressureprocess pipes 60, 70, thereby automatically adjusting the pressure inthe high and low pressure chambers 39, 26 as the process pressuresfluctuate and thus the pressure in the chambers follow the pressurechanges in the high and low pressure process pipes 60, 70. By utilizinga pressure regulator 36 (as shown in FIG. 1F), the pressure on thedownside of the pressure regulator 36 in pressure balancing line 62 willoperate at the set-point of the regulator 36 and thus will not change asthe pressure in the low pressure process pipe 70 changes which mayresult in an undesirable leak direction of the process fluid andlubricant. Particularly during start-up and shut-down conditions, thepressures in the process piping will vary. Also with seasonal changesand ambient air temperatures, the low pressure process pressure willfluctuate and therefore using a regulator may make it difficult toachieve the desired pressure cascade. Without a regulator (as shown inFIGS. 1D and 1E), the PV of the low pressure seals 28 will change as thepressure across the low pressure seals 28 will change with the pressurein the low pressure process pipe 70. This illustrates an advantageousdistinction between using external gases for pressure balancing, as theexternal gases will be controlled by a regulator and will not change asthe pressure conditions in the process change. Also, if the cascadingdirection is toward the process with an external gas, the possibilityexists to leak that external gas into the process.

As shown in the examples of FIGS. 3I and 3J, the pressure balancingconcept can be applied to machines connected to process fluid flowthrough machines in series. The concepts can also be applied toindividual machines that have their process piping connected inparallel. When connected in series, the rotor shafts 14 for each machinecan be individually operated as showing in FIG. 3I, or the rotor shafts14 can be combined to operate a common singular drive shaft 24 asshowing in FIG. 3J.

The pressure balancing can be applied from various points in the processpiping to a chamber or from one chamber to another chamber or from onechamber to another point in the process. As an example, and as shown inFIG. 3I, the high pressure chamber 39 on the higher pressure machine isbalanced with process fluid from high pressure process pipe 60 withpressure balancing line 63. The low pressure chamber 26 a for the first(higher pressure) machine is balanced with process fluid from the mediumpressure process pipe 64 with pressure balancing line 64 a. The processfluid in the medium pressure process pipe 64 is also used to pressurethe high pressure chamber 39 a with pressure balancing line 64 b on thesecond (lower pressure) machine. The low pressure chamber 26 b for thesecond (lower pressure) machine is balanced with process fluid from thelow pressure process pipe 70 with pressure balancing line 72. Asdescribed above, the low pressure chamber 26 a for the first (higherpressure) machine, the high pressure chamber 39 a for the second (lowerpressure) machine, and the low pressure chamber 26 b for the second(lower pressure) machine can be pressure balanced by any source pressure(with or without the assistance of a pressure regulator, if required) inthe process. The resulting pressure will determine the direction of thepressure cascade and the resulting PV effect on the seals. For thetechnique of pressure balancing seals and load shifting to workefficiently, the pressure in each subsequent chamber should be lowerthan the process or the chamber upstream of it such that the chambers oneither side of a seal are designed to leak away from the process towardsatmosphere.

In application of the concepts disclosed, the primary purpose of theseals is to keep lubricant 29 out of the process and to contain thelubricant 29 and process fluid 56 from atmosphere 44. Pressure balancingas described results in achieving the objective by shifting (with theintent of lowering and distributing) the PV factor of the seals in themachine. The role of the sole and primary seal changes from pressurecontainment and lubricant separation to lubricant separation and thepressure containment is shifted to another seal(s).

Directional Flushing of Seals

For seals to work effectively, they must have some leakage, even if itis a very small or trace amount of leakage. The effect of having a verythin layer of lubricant (or process fluid) in the seal interfacedramatically increases the life of the seal and therefore achieving thiseffect and not experiencing any leaking is very unlikely. A single seal,or a set of seals in series, can be arranged to have a balanced pressureacross them or designed to leak in a desired direction by setting up theappropriate pressure differentials so that the leakage through the sealis established to flow from higher pressure to lower pressure.Throughout this document, the term ‘seal’ will mean a single seal or acombination of seals, not necessarily all the same type, working inseries or in parallel to one another.

In the exemplary embodiment of FIG. 2A, the high pressure seals 17, onthe high pressure end of the machine 21, can be designed to leak processfluid 56 from the high pressure side of the machine 21 process into thehigh pressure chamber 39, and then from the high pressure chamber 39into a separator 77, and then to the low pressure process pipe 70,through the pressure balancing lines 73. The process fluid 56 thatpasses from the high pressure chamber 39 into the separator 77 will haveany lubricant 29 removed from the process fluid 56 and that lubricantwill then be drained back into the high pressure chamber 39, and theprocess fluid 56 will pass through pressure balancing line 73 into thelow pressure process pipe 70. Pressure balancing line 73 may or may notcontain a valve, or regulator, whether automatic or manual, that couldaffect the flow rate through pressure balancing line 73, and thus theflow rate of process fluid 56 through the seal(s) 17. Further, FIG. 2Aillustrates an embodiment in which the low pressure chamber 26 acomprises a separator 77 at its outlet. The process side of theseparator 77 vents back into the ORC process through pressure balancingline 53 to a lower pressure than that seen in low pressure chamber 26 afor example, process fluid 56 from this separator 77 can be vented tothe ORC process between the condenser 55 and the process fluid pump 75.Similarly, pressure balancing line 53 may or may not contain a valve,whether automatic or manual, that could affect the flow rate throughpressure balancing line 53, and thus affect the flow rate through theseal(s) 28 a. The separator 77 may be vented to any point in the processthat is at a lower pressure that low pressure process pipe 70, notshown. Pressure balancing line 53 may or may not contain a valve, orregulator, whether automatic or manual, that could affect the flow ratethrough pressure balancing line 53, and thus the flow rate of processfluid 56 through the seal(s) 28 a.

Specifically, a combination of seal arrangements described on the highpressure side of the machine 21 can be utilized on the low pressure sideof the machine 21 as shown in FIG. 2A. The low pressure seals 28 a onthe low pressure end of the machine 21 can be designed to leak processfluid 56 from the low pressure side of the machine 21 process, into thelow pressure chamber 26 a, and then from the low pressure chamber 26 ainto a separator 77, and then through the pressure balancing lines 53,to a point in the process that is at a lower pressure than low pressureprocess pipe 70, such as a pipe or component between the condenser 55and the pump 75.

The seals 17 and 28 can be a single seal or a combination of one ormore: mechanical face seals, lip seals labyrinth seals, dry-gas seals,or any combination thereof. The flow rate through the high and lowpressure seals 17 and 28 can be adjusted to keep leakage flow movingfrom the process into the chambers 39 and chamber 26 a such thatlubricant 29 does not migrate into the process. Too much flow leakagewill compromise efficiency of the machine 21 and too little flow leakagemay risk lubricant 29 migrating into the process. The pressure balancinglines shown 53, 62, 63, 72, and 73, if applicable, can connect to anypoint along the process and do not necessarily have to be connected asshown in FIG. 2A, and pressure differentials should be designed tocascade lubricant flow and process fluid flow from the process toatmosphere. It is not imperative that the flow and pressure cascade downto atmosphere, as pressure equalization also assists, but cascading doesprovide for leak direction. If calculating PV for all seals in a machineset-up, advantages can be shown on PV by having the low pressure chamber26 a at a pressure that is higher than the low pressure end of machine21, and still gain advantage. This would be accomplished by using anintegrated gear mechanism 22 such that the final rotational speed ofdrive shaft 24 was less than that of rotor shaft 14 (a lower ‘V’) andtherefore, with higher pressure across seal 28 b (between chamber 26 aand atmosphere), the resulting PV can still be lower than if no pressurebalancing was applied.

The configuration shown in FIG. 2A is not necessarily restricted toseals that leak from the machine, through the chambers, through aseparator and into the process. This configuration would be suitable forseals that are designed not to leak at a measurable rate.

Load Shifting (Sequential Pressure Chambers)

The PV formula described herein is based on the product of multiplyingP, pressure differential across a seal and the interface velocity Vbetween the static component and the rotating component of the seal.Because changing the speed at which a machine was designed to operate isnot always possible, the only remaining option to reduce PV for a sealis to reduce the pressure differential across that seal. Anotherpossibility would be reduce the shaft diameters of the rotor shaft(s) 14or the drive shaft 24, but doing so would compromise the integrity ofthe shafts. Further, if the concept is to increase the duty of themachine(s), then the rotor shaft(s) 14 and the drive shaft 24 wouldrequire additional capacity, not less with smaller diameter shafts.

The present disclosure relates in one aspect to a method of reducing theproduct of pressure differential and the surface velocity, also known asthe PV factor, experienced by a seal 17, 27, 28 a, 28 b and 28 c, ifapplicable, in a machine 21. The method more preferably involvesshifting the pressure differential to a multiplicity of seals tomanipulate the PV factor from one primary seal location over multipleseals, thereby reducing the PV factor for the primary sole seallocation. The basis of the disclosure is to utilize the processconditions available to reduce the PV factor for the seals 17, 27, 28 a,28 b, and 28 c. The role of the sole and primary seals 17 and 28 achanges from pressure containment and lubricant 29 separation tolubricant 29 separation and the pressure containment such that the PVduty is shifted to other seal(s).

FIG. 3A illustrates an exemplary embodiment comprising a machine 21 withhigh pressure chambers 39 and low pressure chambers 26 a. Although notshown, load shifting the PV is possible with this arrangement. Highpressure seal 17 will not experience load sharing or load shifting, butthe principle of pressure balancing to reduce the PV is applicable,although not shown. Low pressure seal 28 a will load shift the pressuredrop from the low pressure end of the rotating element 20 to lowpressure seal 28 b. Should a double seal 27 be used on the rotor shaft14, the load shifting will be amongst the low pressure seals 28 a and27.

FIGS. 3B, 3D and 3E illustrate various exemplary embodiments of machinesthat have the lowest pressure chamber vented to atmosphere. In theseconfigurations, the lowest pressure chamber is not capable of containingpressure and therefore pressure balancing and load shifting PV acrossthe lowest pressure chamber is not possible. In these exemplarymachines, effectively, one level of the advantages of the disclosure islost. In effect, seal 28 a in FIGS. 3B and 3D does not receive anybenefit of pressure balancing and load shifting PV. In FIG. 3E, thelowest pressure chamber 26 b is vented to atmosphere, but pressurechamber 26 a is suitable for pressure balancing and PV load shiftingseal 28 a.

FIG. 3C illustrates a machine 21 in one exemplary embodiment, similar inpressure containment of chamber 26 a to that shown in FIG. 3A, but withthe addition of an integrated gear mechanism 22 and replacement of adouble seal 27 on the drive shaft 24 with a single seal 28 b. Highpressure chamber 39 is suitable for containing pressure and thereforepressure balancing using a pressure balancing line 63 as shown in theexamples of FIGS. 1D, 1E and 1F. Low pressure chamber 26 a is suitablefor load shifting across low pressure seals 28 a, and 28 b which wouldbe possible with the addition of the pressure balancing line 72 shown inthe examples of FIGS. 1D and 1E, or with the addition of the pressurebalancing line 62 shown in FIG. 1F.

FIG. 3F shows a similar machine 21 to that shown in FIG. 3E under oneembodiment, where two low pressure chambers 26 a and 26 b are shown,where the second pressure chamber 26 b comprises an integrated gearmechanism 22. In FIG. 3F, the low pressure chamber 26 b is not vented toatmosphere as it is in FIG. 3E and therefore that second chamber capableof containing pressure allows for smaller pressure drop increments toget the pressure from the process to atmosphere over more steps.Therefore, should large pressure drops be required from the low pressureend of the machine to atmosphere, several pressure chamber steps willhelp cascade down from the low system pressure seen at process pipe 60,to atmosphere. The PV load shifting of the low pressure seals 28 a, 28b, 28 c will be based on the pressure in the machine 21, the pressure inlow pressure chamber 26 a and the pressure in low pressure chamber 26 b.The PV across the low pressure seals 28 a, 28 b and 28 c, with loadshifting, will be less than the PV of low pressure seal 28 a if loadshifting and function shifting were not applied. The addition of adouble seal 27 at any of the locations is a possibility, with thepreferential location being the last seal before atmosphere. Dependingon the pressure that the pressure balancing lines 53, 62, 72, and 73, ifapplicable, are connected to the process will determine the pressure inthe low pressure chambers 26 a and 26 b, and therefore ultimately affectthe PV across the low pressure seals 28. Should pressure regulators 36be used to reduce the process pressure down before it reaches thepressure chambers, then the PV will be different than if unencumberedwith a regulator 36.

Machines with only a single pressure chamber 26 a are illustrated in theexamples of FIGS. 1C, 1D, 1E, 1F, 2A, 3A, 3C, 3G, 3I, 4A, 4B, 4D, 4E,5A, 5B, 5C, 5D, 5E and 6, where these configurations would be bettersuited to lower pressure drops between process pressure and atmosphere.In a pressure let down application, transmission pipeline operatingpressures are commonly over 1000 psi and distribution systems are under200 psi. Therefore, a double chamber expander, or multiple expanders inseries would benefit from the multi-chamber pressure cascade, whereas anORC application that may only be operating, for example, at 200 psi or300 psi should benefit from pressure differential modifications,provided the face velocity of the seals (based on the diameter of theseals, which are dependent on the shaft diameters) is such that the PVis within acceptable ranges for the commercially available seals.

In a further illustrative embodiment, as shown in FIG. 3F, one or moreseparate low pressure chambers 26 a and 26 b can be used, for example,to isolate the pressure in low pressure chamber 26 a with low pressureseals 28 a and 28 b, and the pressure in lower pressure chamber 26 bwith low pressure seals 28 b and 28 c. In this case, the systemcomprises more than one pressure drop across low pressure chamber 26 aand chamber 26 b in series, such that the pressure differential acrossthe low pressure chambers 26 a and 26 b allows the low pressure seals 28a, 28 b, and 28 c to function within a reduced and workable PV range.Examples will be shown below.

As illustrated in the embodiment of FIG. 3H, low pressure chamber 26 amay be pressure balanced with process fluid 56 from low pressure processpipe 70, whereas lower pressure chamber 26 b could be pressurized byline 53, at another point in the process with lower process fluid 56pressure than found in low pressure process pipe 70, so as to achievepressure cascading such that reduced pressure differential across lowpressure seal 28 b and multi-seal load sharing is achieved. Anothermethod to cascade pressure in the various pressure chambers would be touse pressure regulators to reduce pressure in any said pressure chambersuch that pressure cascading is applied. Should a double seal 27 beemployed at the drive shaft 24, the double seal 27 would alsoparticipate in the pressure reduction arrangement. Should low pressurechamber 26 b be vented to atmosphere 44, then the burden of sealingprocess pressure to atmosphere would be shared between low pressureseals 28 a and 28 b. In one embodiment, illustrated in FIGS. 3G and 3H,a pressure balancing line 63 connects the high pressure process pipe 60and to the high pressure chamber 39, such that the pressure in highpressure chamber 39 approaches the pressure in the high pressure end ofthe machine 21 and that of the high pressure process pipe 60, in orderto reduce the pressure differential on high pressure seal 17.

As an example of the PV of the low pressure seals 28 a, 28 b, in FIG.3H, if the high pressure process pipe 60 was at 180 psi and the lowpressure process pipe 70 was at 50 psi, and if low pressure seal 28 awere the only seal operating to contain the pressure between process andatmosphere, with a typical pressure differential of 50 psi and a sealinterface velocity of 3000 feet per minute, the PV load for low pressureseal 28 a would be 50 psi×3000 feet per minute=150,000. The PV on lowpressure seal 28 b would be 0 psi pressure differential and a sealinterface velocity of 1000 feet per minute would have PV=0.

Similarly, and described in greater detail below in connection with FIG.4C, the pressure balancing techniques must be applied with logic.Specifically, if the pressure in the respective chambers do not cascadedown to atmosphere, the benefit of pressure balancing can be lost. As anexample, if the pressure regulators in lines 62 and 72 were not setappropriately, the pressure in chamber 26 b could be higher than thepressure in chamber 26 a, resulting in leakage of lubricant towards theprocess in place of the leakage away from the process. The followingexample will highlight the case. If high pressure process pipe 60 was at[180] psi and the low pressure process pipe 70 was at [50] psi, and thepressure in pressure balancing line 62 was regulated down to [95] psi(from 180 psi source), and the pressure in pressure balancing line 72were at [40] psi (which has it regulated down from 50 psi to 40 psi),the seal face velocity V for seals on rotor shaft 14 is equal to 3000feet per minute and the seal face velocity V for seals on drive shaft 14is equal to 1000 feet per minute, the PV calculations for the variousseals would be: PV for seal 26 a=(95 psi−40 psi)×3000 feet perminute=165,000 and PV for seal 26 b=(40 psi−0 psi)×1000 feet perminute=40,000.

When using FIG. 4C as an example of progressive cascading pressure dropthrough the machine is applied to the various chambers, the system canbe effective. The following is an example of how not using cascadingpressure drops can be detrimental. Following that example is the exactsame set up but in the second example the use of regulators is used toreduce the PV load on the various seals. Across seal 28 a, the pressureon the process side is 50 psi and pressure in chamber 26 a is 95 psi ifnot pressure reduced in regulator 36, the pressure differential acrossthe seal is 45 psi, and the face velocity V for seals on rotor shaft 14is equal to 3000 feet per minute, the resulting PV equals 135,000towards the process. Across seal 28 b, the pressure in chamber 26 a is95 psi and pressure in chamber 26 b is 40 psi, the pressure differentialis 75 psi, and the face velocity V is equal to 3000 feet per minute, theresulting PV equals 225,000. Across seal 28 c, the pressure in chamber26 b is 40 psi, the pressure differential to atmosphere is 40 psi, andthe face velocity V is equal to 1000 feet per minute, the resulting PVequals 40,000.

Now rearranging the regulator 36 settings to 40 psi in line 62 and 30psi in line 72, the result is:

Across seal 28 a, the pressure on process side is 50 psi and pressure inchamber 26 a is 40 psi, the pressure differential across the seal is 10psi, and the face velocity V for seals on rotor shaft 14 is equal to3000 feet per minute, the resulting PV equals 30,000 towards atmosphere.Across seal 28 b, the pressure in chamber 26 a is 40 psi and pressure inchamber 26 b is 30 psi, the pressure differential is 10 psi, and theface velocity V is equal to 3000 feet per minute, the resulting PVequals 30,000. Across seal 28 c, the pressure in chamber 26 b is 30 psi,the pressure differential to atmosphere is 30 psi, and the face velocityV is equal to 1000 feet per minute, the resulting PV equals 30,000. Theresult is lower PV at all seals, with pressure cascade (and thus flow)towards atmosphere.

The exemplary embodiments of FIGS. 3I and 3J illustrate furtheradvantageous embodiments of the present disclosure. These figuresillustrate the case where the two or more machines 21 are connected inseries to accommodate cascading pressure drop not only in an individualmachine but continuous pressure cascading across multiple machines.These embodiments are particularly advantageous in a pressure let downapplication and could be utilized in a high pressure ORC or steamRankine cycle power generation. The pressure let down applications onpipeline let down would be applicable with hydrocarbon gas utilized inhigh pressure transmission gas pipelines where the gas undergoes apressure drop into low pressure distribution gas pipelines, orapplicable in steam pressure let down applications either in steamsystems or in power generation applications. Although two machines 21are shown, it would be well understood to use two or more machines 21 inseries. It would be understood by a person of skill in the art that twoor more machines 21 can apply the pressure balance technique and loadshifting described above by use of existing higher and lower pressuresthan are in the machine or the process, by utilizing and altering thepressure in the high pressure chambers 39 or each machine as well as inlow pressure chambers 26 a, 26 b or 26 c, if applicable.

The rotor shafts 14 of the multiple cascading machine arrangement may beseparate and directly coupled to multiple loads in expander applicationsand drivers in compressing applications as seen in FIG. 3I, or may beconnected by one or more integrated gear mechanisms 22, as shown in FIG.3J, to a common drive shaft 24, where in an expander application wouldbe connected to a load or in a compressing application connected to adriver. With reference to FIG. 3J, the final gear mechanism containingchamber may or may not be vented to atmosphere as part of pressurebalancing in this chamber and the other chambers in the configuration.These solutions can be applied to a series of machines where the lastmachine in the series can be a condensing machine, with or without theuse of magnetic coupling(s), or applied to a series of non-condensingmachines. Further, the application of a double seal on the output shaftwould prove most beneficial such that the operator would have a visualon the output shaft leaking.

One common feature shown in the examples of FIGS. 3I and 3J are that theconnecting process piping 64 is the discharge side of one machine 21 andthe inlet of the second machine 21 for an expander application and thereverse in a compressor application, thereby allowing the pressure ineach of the adjacent chambers to be pressure balanced by process piping64. This arrangement applies the cascading principle of load sharing,but in place of adjacent chambers on the same machine 21, the highpressure chambers 39 and low pressure chambers 26 a, 26 b and 26 c, asapplicable, are on additional machines in series to the originalmachine.

As an example of the PV of the seals in FIG. 3J, if the high pressureprocess pipe 60 was at 1000 psi and the process pipe 64 was at 350 psi,and the low pressure process pipe 70 was at 150 psi, and a sealinterface velocity of shafts 14 were 3000 feet per minute, and a sealinterface velocity of shaft 24 were 1000 feet per minute, the desirablecascading effect on PV could be:

For the first higher pressure machine in series, the PV on seal 17 wouldbe 0 due to pressure balancing with pressure balancing line 63. The PVfor seal 28 a would be 360,000, based on V=3000 and pressuredifferential=120 psi (where process pipe 64 is at 350 psi and chamber 26a regulated down to 230 psi using pressure balancing line 64 a with aregulator). The PV for seal 28 b would be 390,000, based on V=3000 andpressure differential across 28 b to be 130 psi (based on 230 psi inchamber 26 a and 100 psi in chamber 26 b).

For the second (the lower pressure) machine in series, the PV on seal 17a would be 0 because pressure balancing line 64 b would pressurizechamber 39 a. On the low pressure end of the second machine, the PV forseal 28 c would be 150,000, based on V=3000 and pressure differential=50psi (process pipe 70 at 150 psi and chamber 26 b regulated in pressurebalancing line 72 down to 100 psi). The PV for seal 28 d would be100,000, based on V=1000 and pressure differential=100 psi (100 psi inchamber 26 b and atmosphere).

Speed Reduction of Output Shaft

Because the dimensions of rotors 20 in positive displacement or turbomachines 21 are designed to operate within a range of ratios of lengthand diameter, as well as pressure ratios to optimize efficiency, therotational speed of rotor shaft 14 is typically higher than therotational speed of the drive shaft 24 required for generatingelectricity, which is typically desirable at 50 or 60 Hertz, dependingon the local power grid. With reference to the examples of FIGS. 1D-1E,2A, 3B-3H, 3J, 4B-4D, 4F, 5A-5B, 5E and 6, the present system mayincorporate a torque transfer mechanism, in which an integrated gearmechanism 22 integrally contained in low pressure chambers 26 a or 26 bis used to change the speed of the rotor shaft 14, such that drive shaft24 is of a different speed than rotor shaft 14. The positivedisplacement screw machine 21 shown provides a primary power which istransferred through rotor shaft 14 to the integrated gear mechanism 22in the low pressure chamber 26 a or 26 b.

Generally, if configured as shown in FIGS. 1D, 1E, 3G, 3H, 4A, 4D, 5A,and 5B, without the use of pressure regulators, the pressure across seal28 a will be near equal. With pressure equalization, although thepressure cascade is not necessarily away from the process, it is notpressure cascading towards the process and therefore will not be drivinglubricant into the process. Placing a pressure restriction device suchas a regulator in the pressure balancing lines can insure a lowerpressure in the chambers to which they are connected and therebyestablish the direction of process fluid 56 flow but more importantlyreduce pressure differential across the seal to reduce PV.

By reducing the pressure differential across a seal, the PV may bereduced. Similarly, by reducing the velocity of the interface, the PVcan also be reduced. The following principle shows how using anintegrated gear mechanism 22, the speed of the drive shaft 24 can bereduced and therefore the PV of the low pressure seal 28 b, at the lowerspeed compared to not being slowed, as shown in the examples of FIGS.1D, 1E, 2A, 3C, 3G, 3J, 4B, 4D, 4F, 5A, 5B and 6 can be reduced versusFIGS. 1F, 3F, 3H, 3I, 4A, 4E and 4A where no speed altering is appliedand no benefit to seal 28 b. Therefore, when the desired drive shaft 24speed is known, the machine can be engineered from both ends todetermine the to determine the gear reduction ratio that is required inthe integrated gear mechanism 22. By applying this methodology, pressurebalancing, load shifting and hence PV shifting can be incorporated intoa design to have efficient use of equipment and capital. It is notedthat if the drive shaft 24 were to exit the machine 21 through the highpressure chamber 39, the result would be similar to the above, with thepressure balancing technique, the PV load shifting of the seals on thehigh pressure end of the machine, along with integrated gear mechanism22 in high pressure chamber 39 would demonstrate a similar advantage.

When evaluating the low pressure end of the machine 21, the pressuredifferential across each of the low pressure seals 28 a and 28 b may bethe same or may be varied due to a number of factors; pressure inprocess, pressure in the low pressure chamber 26 a (or in the case ofmultiple chambers, low pressure chamber 26 b), speed of the rotor androtor shafts 14 and drive shaft 24, gear reduction ratio, shaft diameterand speed of rotor shaft 14 relative to shaft diameter and interfacespeed of drive shaft 24. One leading factor is the pressure brought intolow pressure chamber 26 a, relative to the pressure on the lowerpressure end of the rotating element 20, creates the pressuredifferential across the low pressure seal 28 a. This differential can beset to 0 psi differential by matching the pressure on both sides of seal28 a but doing that only shifts the burden to the remaining seals thatare in operation further from the process.

If the pressure in low pressure chamber 26 a is higher than in thepressure in process pipe 70, this is a less advantageous configurationthan if the pressure in low pressure chamber 26 a were lower or equal tothe low pressure process pipe 70. Regardless of the pressure gradientdirection, the lower the pressure differential, the less PV on the lowpressure seal 28 and therefore the less duty the seal has to be able toovercome. Seals installed in a situation where the system is designed tooperate at a pressure in the low pressure chamber 26 a is higher than inthe low pressure process pipe 70, must be designed for the pressuregradient. Meaning, if a seal is designed to work with ID pressure asopposed to OD pressure, it has a different design configuration andconsideration should be given in those circumstances.

As illustrated in the examples of FIGS. 1D, 1E, 2A, 3C, 3G, 3J, 4B, 4D,4F, 5A, 5B and 6 in a case when the speed of the rotor shaft(s) 14 isaltered through use of an integrated gear mechanism 22, and the PVfactor for low pressure seal 28 b is reduced not only by pressurebalancing in the chamber, but also by altered surface velocity of theseal, caused by altering the speed of drive shaft 24 relative to thespeed of rotor shaft 14 through the use of the integrated gear mechanism22. In such case, pressure differential across the low pressure chamber26 b may be less than that at low pressure chamber 26 a. It is notnecessary that the PV value for each seal in the system be equal but itis valuable to reduce PV in seals by shifting the sealing burden acrossmultiple seals. With varying PV's at the various seal locations, acombination of seal types may provide a more robust or more costeffective solution that utilizing the same type of seal throughout themachine 21. Further, the use of a labyrinth seal in a location that issuitable to leak and thus end up pressure balanced by the leakagethrough the seal, may prove cost effective and provide minimal loses dueto friction, as is possible with friction seals. Further yet, the sameseals operated at a lower PV should last longer than the same seals witha high PV, all else being equal. The advantages here are reduceddowntime and reduced maintenance costs. It may be beneficial to loadshare with a single chamber 26 a and place all of the PV onto seal 28 bin place of load shifting the PV. One situation of structuring the PVload in this manner is that the last seal before atmosphere could bereplaced without having to disassemble the machine, whereas the balanceof the seals in the machine would require its disassembly, thereby costand downtime would be encountered whereas it would prove advantageous toload the last seal by making it a sacrificial seal and preserve the lifeexpectancy of the inner seals.

With reference to the exemplary embodiment of FIG. 3D, in the case ofone low pressure chamber 26 a that is open to atmosphere 44, no pressurebalancing may be applied. As an example of the PV of the low pressureseals 28 a, 28 b, if the high pressure process pipe 60 was at 180 psiand the low pressure pipe 70 was at 50 psi, and if low pressure seal 28a were the only seal operating to contain the pressure between processand atmosphere, with a typical pressure differential of 50 psi and aseal interface velocity of 3000 feet per minute, the PV load for lowpressure seal 28 a would be 50 psi×3000 feet per minute=150,000. The PVon low pressure seal 28 b would be 0 psi pressure differential and aseal interface velocity of 1000 feet per minute would have PV=0.

With reference to the exemplary embodiment of FIG. 3C, the following isan example of the benefits of speed reducing the drive shaft 24 relativeto the rotor shaft 14. With the low pressure process pipe 70 contained50 psi process fluid 56, and the low pressure chamber 26 a were pressurebalanced with the low pressure process pipe 70, and if low pressureseals 28 a, 28 b were to load share, the pressure differential acrosslow pressure seal 28 a would be 0 psi with a seal interface velocity of3000 feet per minute, the PV load for low pressure seal 28 a would be 0psi×3000 feet per minute=0. If the drive shaft 24 speed is reduced by aintegrated gear mechanism 22 to 1000 feet per minute, and the pressuredifferential across low pressure seal 28 b would be 50 psi, the PVacross seal 28 b would be 50 psi×1000 feet per minute=50,000, cuttingthe PV to a third of the previous example. By utilizing the pressurebalancing with load shifting concepts with speed reduction of the driveshaft 24, the PV of the previous arrangements higher seal PV will bereduced, extending the life and pressure containing capability of theseal. However, this configuration merely transfers the pressuredifferential, and hence the PV load to low pressure seal 28 b, which isexposed to low pressure chamber 26 a on one side and atmosphericpressure on the other side. The benefit gained here is that drive shaft24 rotates at a slower speed than rotor shaft 14, thereby giving a lowerPV to low pressure seal 28 b that would be at low pressure seal 28 a,proportioned by the amount of the speed reduction. Additionally, thisbeing the last seal before atmosphere, it could be specified to be adouble seal (so that if the seals starts failing, lubricant is lostthrough the seal and not the process fluid) and structured to be asacrificial seal and thereby reducing maintenance costs and downtime.

With reference to FIG. 1A, in the case of only one low pressure seal 28a in a singular low pressure chamber 26 a vented to atmosphere 44, andone high pressure seal 17 in a singular high pressure chamber 39, thepressure across low pressure seal 28 a goes from process pressure toatmospheric, a typical pressure differential being 50 psi and a typicalPV load being 50 psi×3000 feet per minute=150,000 and the pressureacross high pressure seal 17 goes from process pressure to atmospheric,a typical pressure differential being 180 psi and a typical PV loadbeing 180 psi×3000 feet per minute=540,000. In order to equalizepressure on either side of the machine 21, the high pressure chamber 39and the low pressure chamber 26 the vents must first be closed, asillustrated in FIG. 1C, allowing low pressure chamber 26 a and 39 to bepressurized, preferably by connection via pressure balancing line 63 tothe high pressure process pipe 60 and 72 to the low pressure processpipe 70 (as shown in FIG. 3G). The low pressure seal 28 a pressuredifferential, P, then becomes 0 and the PV for low pressure seal 28 abecomes 0 and the high pressure seal 17 pressure differential, P, thenbecomes 0 and the PV for the high pressure seal 17 becomes 0.

Alternatively, in one embodiment that does not provide any advantage isthe addition of low pressure chamber 26 b as shown in FIG. 3E, relativeto the arrangement shown in FIG. 3F. In FIG. 3E, the low pressurechamber 26 a is now sealed and a second low pressure chamber 26 b isvented to atmosphere 44, along with the addition of low pressure seals28 b, 28 c to the system, allows the total pressure drop otherwiseexperienced by low pressure seal 28 a would appear to be split overmultiple seals. The shaft speed within the first chamber 26 a and thesecond chamber 26 b is not altered and V remains at 3000 feet perminute. Pressure balancing, by increasing the pressure in low pressurechamber 26 a to 50 psi leads to a pressure difference across lowpressure seal 28 a of 0 psi and a PV of 0. The pressure differentialacross low pressure seal 28 b becomes (50 psi−0 psi at atmosphere) 50psi, and a PV of 50 psi×3000 feet per minute=150,000. The PV factor forlow pressure seal 28 c is zero because low pressure chamber 26 b isvented to atmosphere 44, resulting in a pressure differential of 0.Therefore, the PV limit of 150,000 that was shown for low pressure seal28 a, when it was the only seal, remains the same but only shifts theload to seal 28 b. If chamber 26 b were to be closed to atmosphere asshown in FIG. 3F, the load could be distributed amongst multiple seals(depending on the pressure of the process fluid that is brought into thepressure chamber), and the PV calculations show: seal 28 a, PV=0 becauseof pressure balancing chamber 26 a to process pipe 70 yields a 0pressure differential, and with chamber 26 b being pressurized to say 30psi, the pressure differential on seal 28 b is now 50 psi−30 psi, thepressure differential is now 20 psi×3000 feet per minute=60,000. And thePV of seal 28 c becomes 30 psi×1000 feet per minute for drive shaft 24,equaling 30,000 PV. Thereby demonstrating pressure cascade, and PV loadsharing with the benefit of gear reduction to the drive shaft 24. Moreimportantly it is not so much the total PV amongst the seals as it is tolower the PV of the previous arrangements of the high PV of the singleseal(s).

Due to the potentially varying nature of shaft velocity, the reductionin P (pressure differential) achieved by the present pressure balancingsystem need not be large to result in a significant and desirable dropin PV or seal life extension. It is to be noted that by splitting thesealing duty to multiple locations, the sum of the individual PV on eachseal does not necessarily add to the original PV. Both P and V can bevaried to achieve the desired effect and such variations would be wellunderstood by a person of skill in the art to be encompassed by thescope of the present disclosure.

In another exemplary embodiment, two separate low pressure chambers 26a, 26 b may contain an integrated gear mechanism 22 for reducing speedof drive shaft 24. In these embodiments, pressure balancing of the firstlow pressure chamber 26 a can be accomplished by connecting line 62(with a pressure regulator to high pressure process pipe 60) to chamber26 a either to the high pressure process pipe 60, as is shown in FIGS.1F 4B, and 4C, or to the low pressure process pipe 70, as in the case ofFIGS. 1D, 1E, 3G, 3H, 4A, 4D, 5A, 5B, and 6 via a pressure balancingline 72, or as in the case of FIGS. 3I, 3J, 4E, and 4F via a pressurebalancing line 64. Should the connection be made to the high pressureprocess pipe 60, it may more preferably be passed through a pressureregulator 36 to lower process fluid pressure in low pressure chamber 26a, while remaining at a higher pressure than the pressure in lowpressure chamber 26 b which will cause the lubricant 29 from lowpressure chamber 26 a to be forced into the seal interface.

This pressure cascading configuration is more desirable, but notabsolutely necessary, to have leakage flow in the direction away fromthe process and towards atmosphere than the opposite of having lubricant29 pushed into the process. Similarly, as shown in FIG. 3H, where lowpressure chamber 26 a is pressure balanced from low pressure processpipe 70, lower pressure chamber 26 b would pressurized by line 53,another point in the process with pressure lower than low pressureprocess pipe 70 to achieve reduced pressure differential across lowpressure seal 28 b and multi-seal load sharing. Should low pressurechamber 26 b be vented to atmosphere 44, then the burden of sealingprocess pressure to atmosphere would be shared between low pressureseals 28 a, 28 b. In another advantageous configuration, a double seal27 may be placed on the drive shaft 24 because its speed would be lowerthan the rotor shaft 14.

Pressurized Lubricant Circulation Systems

FIG. 4A illustrates an exemplary embodiment comprising machine 21 with ahigh pressure chamber 39 on the high pressure side and chamber 26 a onthe low pressure side, without an integrated gear mechanism 22, andwithout a circulating lubricant circulation system. The low and highpressure chambers 26 and 39 respectively, contain lubricant 29 in thebottom of each chamber. This is referred to as splash lubrication as itdoes not have a circulating pump to distribute the lubricant. It is thesimplest form of lubricant circulation systems and may be suitable incircumstances where the bearings do not have heavy loads. Pressurebalancing and load shifting is appropriate with this type of lubricationbecause the heat generated by the seals will be lower than if all of theload were on seal 28 a.

FIG. 4B illustrates an exemplary embodiment comprising machine 21similar to the one in FIG. 4A, where this machine 21 has a single highpressure lubricant circulation system 30, comprising of lubricantcirculation pump 45, lubricant lines (shown as part of lubricantcirculation system 30), heat exchanger 32, lubricant 29, pressureregulator 36, and reservoir with heat exchange and separationcapabilities 35. To accommodate the pressure from the pressure balancingmechanisms described above into each of the high pressure chamber 39 andlow pressure chambers 26 a, and 26 b, lubricant 29 can be circulated andrecovered from both the high and low pressure chambers 39, 26 a, 26 band then recirculated. The lubricant 29 would leave lubricantcirculation pump 45 at a higher pressure than process fluid 56 wouldhave in process piping 60, the pressure used to pressure balance chamber39. In addition to providing lubrication to the bearings 16, 66, 88, thelubricant 29 serves the purpose of removing heat from the seals 17, 28a, and 28 b. The pressure cascade will drive the lubricant from thehigher pressure chambers to the lower pressure chambers, to whicheventually, the lubricant will drain back to the reservoir 35 to feedthe circulating lubricant circulation pump 45.

As shown in the examples of FIGS. 4B and 4C, it is possible to useprocess vapor pressure differential from the high pressure chamber 39 tothe low pressure chambers 26 a in the case of FIG. 4B and to chamber 26a first and then to chamber 26 b in the case of FIG. 4C, to make thelubricant flow from the higher pressure to the lower pressure chamber.As an example, process fluid 56 from the high pressure process pipe 60can be directed to the high pressure chamber 39 by a pressure balancingline 63 or by leaking through high pressure seal 17 from the highpressure sides of the machine 21 to the high pressure chamber 39. Thiswould then pressurize the high pressure chamber 39 and the high pressurelubricant circulation system 30, which the lubricant circulation system30 would operate at a higher pressure to drive lubricant into chamber39. The lubricant circulating lines (shown as part of lubricantcirculation system 30) would then transfer the lubricant at thatpressure, through a pressure regulator 36 and a heat exchanger 32, ifrequired, to low pressure chamber 26 a. The pressure differential iswhat would make the lubricant flow from the higher pressure to the lowerpressure chamber.

The exemplary embodiment of FIG. 4C illustrates two low pressurechambers, 26 a and 26 b. Pressure balancing to chamber 26 a is appliedfrom high pressure process pipe 60, passed through a regulator 36 inpressure balancing line 62, to chamber 26 a. Pressure balancing tochamber 26 a is applied from high pressure process pipe 60, passedthrough a regulator 36 (to be set at a higher pressure setting fromprocess pipe 70 pressure) in pressure balancing line 62, to chamber 26a. Pressure balancing to chamber 26 b is applied from low pressureprocess pipe 70, passed through a regulator 36 (not necessarily requiredprovided pressure regulator in line 62 is at a higher pressure settingfrom process pipe 70 pressure) in pressure balancing line 72, to chamber26 b. The concept being that the setting on the regulators is such thata cascading pressure drop is established between the process pressure atthe machine and atmosphere. The cascading pressure drop facilitates thelubricant flow from the initial chamber 39, to chamber 26 a, to chamber26 b, to the reservoir 33, reservoir with heat exchange capability 34,or reservoir with heat exchange and separation capabilities 35, or anycombination thereof, as the case may be.

FIG. 4D, illustrates a machine 21 configuration which comprises anintegrated gear mechanism 22, a high pressure lubricant circulationsystems 30, comprising of lubricant circulation pump 45, lubricant lines(shown as part of lubricant circulation system 30), lubricant 29,pressure regulator 36, and reservoir with heat exchange capability 34,and a low pressure lubricant circulation systems 31 comprising oflubricant circulation pump 54, lubricant lines (shown as part oflubricant circulation system 31), lubricant 29, pressure regulator 36,and reservoir with heat exchange capability 34. Pressure balancing thehigh pressure chamber 39 with lines 63 and pressure balancing the lowpressure chamber 26 a with pressure balancing line 72, are beingapplied. FIG. 4B shows a similar configuration, however with a singularhigh pressure lubricant circulation system 30 in which lubricant 29 fromthe high pressure chamber 39 passes through a pressure regulator 36before being supplied, and being temperature adjusted, if required, tolubricate the bearings 66 and 88 and low pressure seals 28 a and 28 b.Lubricant 29 from low pressure chamber 26 a may be temperature adjustedand then temporarily stored in the reservoir 33 or reservoir with heatexchange capability 34 or reservoir with heat exchange and separationcapabilities 35, before being recirculated through the high pressurelubricant circulation system 30. Pressure balancing the high pressurechamber 39 with lines 63 and pressure balancing the low pressure chamber26 a with pressure balancing line 62, are being applied.

In one embodiment, as shown in FIG. 4C, lubricant 29 from the highpressure chamber 39 is passed through a pressure regulator 36 prior tobeing circulated through a heat exchanger 32, if required, and then tothe low pressure chamber 26 a, which can then further circulate toadditional low pressure chambers 26 b, before being temperature adjustedin the reservoir with heat exchange and separation capabilities 35 andthen to lubricant circulation pump 45 to circulate the lubricant throughthe lubricant circulation system 30.

Numerous variations to the lubricating method and high and low pressurelubricant circulation systems 30 and 31 described above are possible andencompassed by the scope of the present disclosure. For example, asillustrated in FIG. 4D, the system may have separate high and lowpressure lubricant circulation systems 30 and 31 connected to each ofthe high pressure chambers 39 and low pressure chambers 26 a (and 26 b,if applicable). In this case, a separate high pressure lubricantcirculation system 30 comprising a high pressure heat exchanger 32 (notshown) and a high pressure reservoir with heat exchange and separationcapabilities 35 can supply lubricant 29 to the high pressure seals 17,bearings 16 and gears 40 in chamber 39. The separation of the high andlow pressure lubricant circulation systems 30 and 31 has advantagessince the separate systems will operate at the respective pressures towhich they are pressure balanced from. In the case of the high pressurebalancing line 63 the respective pressure will be the pressure in highpressure process pipe 60 and for the low pressure balancing line 72, thepressure in low pressure process pipe 70.

Another feature is that the high pressure chamber 39 may have steadierpressure than the low pressure chamber 26, which may experience pressurefluctuations in the process system. Since the high pressure lubricantcirculation system 30 must provide sufficient pressure to overcome thepressure in high pressure chamber 39 and the low pressure lubricantcirculation system 31 must provide sufficient pressure to overcome thepressure in low pressure chambers 26 a or 26 b, as the case may be,utilizing a single lubricant system for both chambers simultaneously canpose challenges and could require the use of regulators, and possiblycontrol valves. Dedicated lubricant systems for each set of chambersovercome these challenges. Pressure balancing the chambers with therespective pressure piping also allows the PV across the first set ofseals between the process and the first chamber to automatically adjustto a balanced pressure, thereby reducing the risk of lubricant makingits way into the process. Restated, the advantage of the split systemsis that the individual lubricant circulation system pressures willfluctuate with changes in the process pressures, thereby not distortingthe lubricant flow rate if one lubricant circulation system were beingutilized and the higher pressure process fluid 56 in pipe 60 werefluctuating relative to, and independently, to lower pressure processfluid 56 in pipe 70.

By separating the high and low pressure lubricant circulation systems 30and 31 into lubricant circulation pump 45 for the high pressure side andlubricant circulation pump 54 for the low pressure side, each lubricantsystem will operate at a reasonable pressure (40 to 60 psi) over thebalancing pressure. By designing separate high and low pressurelubricant circulation systems 30 and 31 with lubricant circulation pumps45 and 54 respectively, the pumps will deliver the required flow rate oflubricant to the seal, bearings and gears, which operate on adding apressure differential to the lubricant 29 pressure between the pumpinlet and pump discharge, where the pump inlet is the pressure in thechamber to which the lubricant 29 drains from, and thus the challenge ofinsuring enough lubricant 29 flow to the high pressure seals 17 and lowpressure seals 28 a, 28 b, 28 c, and bearings 16, 66, 88, due to varyingpressure differential across the machine 21 and hence the high pressurechamber 39 and low pressure chambers 26 a and 26 b, and bearings 16 and66, is eliminated.

Furthermore, a separator 77 as shown in the exemplary embodiments ofFIGS. 1E, 2A, 5A and 5B, and reservoir with heat exchange and separationcapabilities 35 as shown in FIGS. 4B, 4C, 4E, 4F, or reservoir with heatexchange capability 34 in FIGS. 4D, 5A, 5B and 6, may prevent lubricant29 from migrating into the process and will collect the coalescedlubricant back into the respective high pressure chamber 39 and lowpressure chambers 26 a and 26 b as the case may be, to the reservoir 33,34 or 35 to allow the separation of the lubricant from the process fluid56. An optional vapor recovery unit (not shown) may also be added to anypressure balancing lines 53, 62, 63, 72, and 73, to facilitate theseparation of process fluid 56 from the lubricant 29.

In a further exemplary embodiment, the present disclosure need notinclude an external lubricant circulation system 30 at all. Insteadlubricant 29 may be stored in sumps, as shown in FIGS. 1A-1F, 2A, 3A-3J,4A, 5C, 5D and 5E, on either the high pressure chamber 39 or the lowpressure chamber(s) 26 a and 26 b, or both, should it be applicable. Insuch cases, temperature control of the chambers can be supplied by anoptional external jacket medium (not shown) or air flow provided aroundthe chambers. Possible fluids for temperature adjustment can be processfluid 56, water, glycol, thermal oil or air.

Similar to the single lube oil system shown in the exemplary embodimentsof FIGS. 4B and 4C, a similar concept is shown in FIGS. 4E and 4F. Asingle lubricant circulation system, with a single lubricant circulationpump 45, is shown to provide lubricant to two machines in series. Thecascading pressure drop of the chambers (containing seals, bearings andgears, as the case may be) set up in the machines facilitates thedistribution of lubricant throughout the machines, through a series ofpressure regulators, heat exchangers and pressure chambers. Becausepressure balancing is being utilized from three sources, process pipe60, 64 and 70, separate lubricant circulation systems for the 3operating pressure levels may be better suited to the concept.Therefore, chamber 39 in machine number one, pressure balanced byprocess pipe 60 would have a lubricant circulation system operating atthat pressure plus the required pressure differential from the pump ofsay 40 psi. Chamber 26 a in machine number one and chamber 39 a ofmachine number two would be pressure balanced by pressure balancinglines 64 a and 64 b from process pipe 64 and therefore would have alubricant circulation system operating at the pressure of process pipe64 plus the required pressure differential from the pump of say 40 psi.The third lubricant circulation system would also operate at pressureand provide lubrication to the bearing and seal components in chamber 26b in the case of FIG. 4F and chamber 26 b of the second machine in thecase of FIG. 4E. Neither of the multiple lubricant circulation systemconfiguration is shown in full detail, for the sake of brevity. Oneskilled in the art would recognize that the configurations describedabove are equally applicable to multiple lubricant circulation systemshaving expanders/compressors in series. Similarly, for the sake ofbrevity, if the pressure through the series of machines is higher than aseal is capable of handling at the respective PV for the arrangement, anadditional pressure chamber may be added to assist in cascading thepressure down towards atmosphere. As an example, in FIG. 4E, if processfluid 56 in process pipe 60 were at 1000 psi, then it would bereasonable to expect the pressure in pipe 64 to be approximately 350psi. Therefore, the pressure differential between the low pressurechamber in the first higher pressure machine and atmosphere would be 350psi to be distributed over seals 28 a and 28 b. This may provechallenging and therefore with the addition of a third chamber 26 c (notshown), that would be appended to chamber 26 a, the pressuredifferential can be reduced over seals 28 a, 28 b, 28 c, and 28 e (notshown). Thereby with effective pressure balancing of chambers 26 a, 26b, and 26 c the PV of the seals could be significantly improved. Foradded protection, a double seal could be installed on rotor shaft 14 ofthe first higher pressure machine. Changing the configuration to utilizean integrated gear mechanism 22, as shown in FIG. 4F, would accomplishthis effort. If this later configuration still proved too much for thecapability of standard seals, then an additional pressure chamber on thefirst higher pressure machine (between the first chamber and theintegral gear box), could be added.

Sealing Output Shafts

The exemplary methods and systems of the present disclosure can beapplied to seals of any number of configurations in the machine 21. Withreference to FIGS. 1A-1F, 2A, 3A-3J, 4A-4F, 5A-5E, and 6, these conceptswill apply in any combination. In any of the figures disclosed herein,the high pressure seals 17 and low pressure seals 28 a (and 27, ifapplicable), provide a first means of preventing loss of process fluid56 from the machine 21.

As is shown in the advantageous embodiment of FIG. 3A, a double seal 27is installed on the rotor shaft 14. Use of double seal 27 at thislocation has advantages in that a pressurized double seal 27 requires ahigher pressure medium to be injected into the cavity between the twoseals within the double seal so that if one of the two seals withindouble seal 27 leaks, it leaks the higher pressure medium fluid and notthe process fluid 56 to atmosphere 44. FIG. 3A has a splash lubricationsystem and therefore the combination utilizing a pressurized double sealis highly unlikely, but may be utilized with a non-pressurized doubleseal.

As shown in the exemplary embodiments of FIGS. 5A and 5B, a machine 21with an integrated gear mechanism 22, a high pressure lubricantcirculation system 30, a low pressure lubricant circulation system 31,with a pressurized double seal 27 installed on the drive shaft 24. Thehigh pressure lubricant circulation system 30 has a pressure balancingline 63 and passes through a separator 77. The lubricant circulationsystem 30 is controlled by the control module 93 (shown in FIG. 6) andhas a vent line tied into the pressure chamber 39 (or alternativelydirectly into separator 77). The lubricant 29 drain line from theseparator runs into the high pressure chamber 39 (alternatively into thereservoir 33, reservoir with heat exchange capability 34, or reservoirwith heat exchange and separation capabilities 35). Similarly, the lowpressure lubrication system 31 has a pressure balancing line 72 andpasses through a separator 77. The lubricant circulation system 31 isalso controlled by the control module 93 (shown in FIG. 6) and has avent line tied into the pressure chamber 26 a (or alternatively directlyinto separator 77). The lubricant 29 drain line from the separator runsinto the pressure chamber 26 a (alternatively into the reservoir 33,reservoir with heat exchange capability 34, or reservoir with heatexchange and separation capabilities 35). The lubricant circulationsystem 31 would be controlled by the control module 93 (shown in FIG. 6)and it has reservoir with heat exchange capability 34 that could alterthe temperature of the lubricant to keep it in the desired range, alsocontrolled by control module 93.

As shown in the exemplary embodiment of FIG. 5A, the lubricant 29supplying the pressure to the double seal 27 is provided by the lowpressure lubricant circulation system 31. In this application, thelubricant 29 that is used on the low pressure process piping end of themachine 21, from the low pressure lubricant circulation system 31, willbe at a higher pressure than the low pressure chamber 26 a because thelubricant 29 must flow and the lubricant circulation pump 54 providesthe pressure differential to make the lubricant flow. The lubricantcirculation pump 54 experiences the low pressure chamber pressure at itsinlet and the lubricant circulation pump 54 creates an increasedpressure differential to circulate the lubricant 29. The resultinghigher pressure of the lubricant 29 will be used to charge the cavity inthe pressurized double seal 27. Therefore, if either side of the doubleseal 27 leaks, it will leak lubricant into the low pressure chamber 26 aor lubricant to atmosphere 44.

As shown in the exemplary embodiment of FIG. 5B, the lubricant 29 fromthe high pressure lubricant circulation system 30 is utilized to chargethe cavity in the double seal 27, similarly, when either side of thedouble seal 27 leaks, it will leak lubricant 29 into the low pressurechamber 26 a or lubricant 29 to atmosphere 44. The inner side of thepressurized double seal 27 will leak lubricant 29 into the low pressurechamber 26 a (which already has lubricant in it) or if the outer side ofthe double seal 27 leaks, it will leak lubricant 29 to atmosphere 44.This will provide a visual indication to an operator that the doubleseal 27 is leaking which will then draw the necessary maintenance.Without the double seal 27, a single seal could fail and the entiresystem charge could be lost to atmosphere without indication. Clearly,lubricant 29 from lubricant circulation system 30 will be at higherpressure than chamber 26 a and therefore will provide an effectivemedium to charge the cavity between the two seals in the double seal 27.The lubricant circulation pump 45 experiences the high pressure chamberpressure at its inlet and the lubricant circulation pump 45 creates anincreased pressure differential to circulate the lubricant 29. Theresulting higher pressure of the lubricant 29 will be used to charge thecavity in the pressurized double seal 27.

In another exemplary embodiment of the drive shaft 24 sealing technique,the purpose of this seal is used to prevent the machine 21 from leakingprocess fluid to atmosphere or allowing ambient air to enter the processthrough the machine 21. This can also be accomplished by incorporating amagnetic coupling to the rotor shaft 14, as shown in FIGS. 5C and 5D, orto the drive shaft 24, as shown in FIG. 5E, such that the machine 21becomes hermetically sealed from the atmosphere.

The magnetic coupling system as illustrated in FIG. 5D, is generallycomprised of items 11, 12, and 13. It will be referred to as a magneticcoupling system assembly 46 as shown by the dashed line in FIG. 5C. Themagnetic coupling is shown in FIGS. 5C, 5D, and 5E. The magneticcoupling system assembly 46 is shown with magnetic coupling output shaft10, which replaces the function of shafts 14 or 24, as the case may be.The magnetic coupling provides a degree of inherent safety, such that amachine 21 with a magnetic coupling can be used with a multitude offluid mediums in expansion, including natural gas or steam in pressurelet-down applications, and with a full range of process fluids inorganic Rankine cycle systems, or in compression, including natural gasor refrigerant. Also, such configurations prevent atmosphere 44 fromentering the machine 21 and potentially contaminating the process fluid56.

With reference to exemplary embodiments illustrated in FIGS. 5C and 5D,a simplified torque transfer mechanism is shown. Intermeshing male andfemale rotors 19 and 20 may rotate in opposite directions relative toone another and may be contained within the expander 21 supported byhigh speed low/high pressure bearings 16 and 66. These rotors, 19, 20intermesh and create a cavity in between the rotors allowing processfluid to expand as the cavity volume increases along the length of theinterface between the rotors 19 and 20 as the rotors rotate relative toone another. Machine 21 provides a primary shaft power which istransferred from the male magnetic coupling end 13, through the magneticcoupling shroud 12, to the female magnetic coupling end 11. Thecomponents of the magnetic coupling are the female torque transfer hub11, the shroud 12, and the male torque transfer hub 13.

The male torque transfer hub 13 is connected to the rotor shaft 14, alsoreferred to as an extended rotor shaft. The female torque transfer hub11 is connected to the magnetic coupling output shaft 10, of themachine. The role and function of rotor shaft 14 is the same as that ofdrive shaft 24, with the exception that drive shaft 24 is expected to berotating at a slower speed. It may be advantageous not to speed reducedrive shaft 24 relative to rotor shaft 14 as the torque increases as thespeed reduces and magnets have a torque limit before they start slippingagainst one another, therefore, application of the magnetic couplingsystem assembly 46 may be applied to drive shaft 24 with or withoutspeed reduction, if not only to enable pressure balancing principle withuse of a chamber, as shown in FIGS. 5C, 5D, and 5E.

The magnetic coupling shroud 12 is hermetically sealed to the machine21, preventing process fluid 56 from escaping the machine 21, andpreventing atmosphere 44 from entering the machine 21. End cover platesof the high pressure chamber 39 and low pressure chambers 26 a and 26 bact in a similar manner to the magnetic coupling shroud 12 to containthe process fluid 56 within the machine 21, and prevent atmosphere 44from entering the machine 21. The magnetic coupling in a way replicatesthe configuration shown on the high pressure chamber 39 of the machine21, and therefore the solutions proposed to that end of the machine 21become applicable to the low pressure end of the machine with a magneticcoupling attached to either rotor shaft 14 or drive shaft 24.

In one particularly advantageous embodiment, the present system providesa pressure balancing system applicable with a magnetic coupling on atwin screw expander drive shaft 24, such as that illustrated in FIGS.5C, and 5D. With reference to these figures, the system comprises amachine 21, a rotor shaft 14 and a magnet coupling system assembly 46comprising a shroud, and a magnetic coupling to transfer shaft torquewith matched speed on both sides of the magnetic coupling. The magneticcoupling system assembly 46 can be incorporated at the rotor shaft 14or, if an integrated gear mechanism 22 is used as shown in FIG. 5E, withdrive shaft 24. The rotor shaft 14 typically rotates at a higher speedand lower torque than the drive shaft 24. A magnetic coupling systemassembly 46 integrated onto the drive shaft 24 would experienceapproximately the same horse power but at lower speed with highertorque. Therefore, for the application a magnetic coupling systemassembly 46 affixed to the rotor shaft 14 rather than to the drive shaft24 is also a suitable arrangement.

The challenge with implementing the magnetic coupling system assembly 46at the drive shaft 24 is the generation of heat, equivalent to an energyloss, by induced eddy currents. Reducing eddy currents reduces heat andenergy loss and thereby increases efficiency of the machine 21.Similarly, heat generated by friction on the seals is a loss in energyefficiency and the objective is to design a seal with minimal energyloss but suitable to accomplish the sealing objective described above.

The alternating magnetic fields produced by a rotating magnetic couplingsystem assembly 46 generate eddy currents in conductive materials. Eddycurrent generation increases with increased rotational speed. To preventheat generation and energy loss, non-conductive, non-metallic shroudscan preferably be incorporated into the magnetic coupling. Mostadvantageously, the magnetic coupling shroud 12 can be made of ceramicmaterial or any other non-conductive material that does not produce anysignificant eddy currents.

A magnetic coupling system assembly 46 on the drive shaft 24 ispreferably larger in size than a magnetic coupling system assembly 46 onthe rotor shaft 14 because if drive shaft 24 is rotating slower thanrotor shaft 14, it will need to transfer the same amount of power andtherefore will require increased torque capabilities. All magneticcouplings have a breakaway torque at which the magnets will sliprelative to one another; therefore, the coupling is preferably sized forequal or more than the amount of power to be transferred through themagnetic coupling. In one embodiment, the magnetic coupling systemassembly 46 is not a concentric cylindrical magnetic coupling butcomprises two circular, parallel flat plate magnetic couplingstransferring rotational torque through a flat membrane material situatedbetween the two circular, parallel flat plate magnets.

Heating Vs. Cooling Lubricant

The lubricant 29 temperature can be adjusted in heat exchanger 32,reservoir with heat exchange capability 34, or reservoir with heatexchange and separation capabilities 35, along with air flow over theequipment. For the purposes of this section, a ‘heat exchanger’ willrefer to any or all of heat exchanger 32, reservoir with heat exchangecapability 34, or reservoir with heat exchange and separationcapabilities 35. The temperature of the lubricant 29 can be altered byapplying air exchange or liquid exchange through an appropriate heatexchanger. In circumstances, such as cold starting of the processsystem, where the lubricant 29 is colder than the air temperature, thelubricant 29 will be heated in an air exchanger. In circumstances, suchas during operating, the air temperature will typically be cooler thanthe lubricant 29 and therefore in an air exchanger, the lubricant 29will be cooled. In circumstances, such as cold starting of the processsystem, where the lubricant 29 is colder than the liquid on the otherside of a liquid heat exchanger, such as a shell and tube heat exchangerthat may contain glycol from the process, the lubricant will be heatedin that heat exchanger. In circumstances, such as during operating,where the lubricant 29 is warmer than the liquid on the other side of aliquid heat exchanger, the lubricant 29 will be cooled.

In the case of the machine 21 being an expander in an organic Rankinecycle application, the liquid on the other side of the liquid heatexchanger could be water, glycol or thermal oil. Depending on thelubricant 29, process fluid 56, ambient air temperatures and processconditions, the heat exchanger(s) may be required to add heat to thelubricant 29 rather than removing heat from the lubricant 29. By keepingthe temperature of the lubricant 29 above the vaporization temperatureof the process fluid 56, this will prevent the process fluid 56 fromcondensing in the lubricant 29 and thus diluting the lubricant 29.

If the high or low pressure chambers 39, 26 a, or 26 b, on the machine21 are large enough, they can serve as the reservoir 33 or the reservoirwith heat exchange capability 34 capabilities, or the reservoir withheat exchange and separation capabilities 35. Depending on thetemperature of the lubricant 29 and the pressure in the high and/or lowpressure lubricant circulation system 30, 31 and high and/or lowpressure chambers 39, 26, it may be advantageous not to cool thelubricant 29 such that the process fluid 56 remains in a vapor state.For cold starts, it may be a requirement to heat the lubricant 29 so asto reduce viscosity so that it can be circulated within the operatingparameters of the lubricant circulation pump 45 or 54 as the case maybe.

In virtually all circumstances with a high and/or low pressure lubricantcirculation system 30 or 31, the lubricant 29 will be drained to areservoir 33, 34 or 35 prior to being circulated back to lubricate thebearings 16, 66 and 88, and high and low pressure seals 17, 28 a, 28 band 28 c. Reservoir 33 may or may not contain heat exchangecapabilities, as well as separation of liquid and vapor capabilities.

As shown in the exemplary embodiment of FIG. 4B, heat exchanger 32,which is positioned between the lubricant circulation pump 45 andchamber 39, could have heat being added to the lubricant 29 so that anyprocess fluid 56 that may have ended up in chamber 39 from pressurebalancing would be vaporized. The lubricant 29 then flows throughlubricant circulating line from high pressure chamber 39 to low pressurechamber 26 a. Along the route, the lubricant 29 may pass through apressure regulator 36 and/or a heat exchanger 32, where the lubricant 29may be heated or cooled as required. The lubricant 29 would then beutilized in low pressure chamber 26 a to lubricate the bearings 66, 88and seals 28 where it would then drain to the bottom of chamber 26 a, tothen pass through lubricant circulating line to the reservoir with heatexchange and separation capabilities 35. At this stage, the lubricant 29may be heated or cooled, depending on the relative temperatures of thelubricant 29 and the liquid heat exchange medium. The flow of heatexchange medium may be controlled by the control module 93 (shown inFIG. 6).

An application that is of particular interest is where a glycol sourceis temperature conditioned to be consistently in a tight temperaturerange. Depending on the temperature of the glycol source, it could proveto be an excellent match to the lubricants 29 operating temperaturerequirements. Specifically, a reciprocating engines glycol can beconsistently supplied at approximately 185 degrees Fahrenheit, dependingon the thermostat settings. If the minimum temperature of the lubricant29 is to be 170 degrees Fahrenheit the glycol will heat the lubricant 29in a heat exchanger 32, reservoir with heat exchange capability 34 orreservoir with heat exchange and separation capabilities 35, and draw itup towards the 185 degree Fahrenheit temperature. At the same time, ifthe lubricant 29 temperature starts to climb over the 185 degreesFahrenheit, the glycol will then work to cool the lubricant 29. Theprocess automatically balances the lubricant 29 temperatures to thedesired condition or the process fluid 56 being in vapor state and thelubricant 29 not being too hot and thereby having reduced viscosity (andhence reduced lubricity that would detrimentally affect the longevityand well being of bearings 16, 66, and 88).

As shown in FIG. 4D, high pressure lubricant circulation system 30 andlow pressure lubricant circulation system 31 are shown; one for the highpressure end of the machine 21 and a second for the low pressure end ofthe machine 21. Heat exchangers 32 (not shown), or reservoirs with heatexchange capabilities 34, or reservoirs with heat exchange andseparation capabilities 35 (not shown) would be utilized to adjust thelubricant 29 temperature to a desired range.

Control Module

In one advantageous embodiment, the present seal system can becontrolled by a control system that is either independent or part of theexisting application, for example as part of an ORC or pressure let downcontrol system. In a further advantageous embodiment, control of thepresent sealing system is controlled by the control system of an ORCunit as described in Applicant's co-pending US Pat. Pub. No.2009/0320477 and US Pat. Pub. No. 2010/0018207, each of which isincorporated by reference in its entirety herein. In such an embodiment,as shown in FIG. 6, monitoring of process fluid pressure, temperature,or flow in process piping 60, 64 or 70, chamber 39, 26 a or 26 b,lubricant in lubricant circulation systems 30, 31, or flow of air orliquid to the heat exchangers 32, reservoirs with heat exchangecapability 34 or reservoirs with heat exchange and separationcapabilities 35. In addition, the embodiment of the control module wouldcontain control of devices such as control of valves 38, 95, lubricantcirculation pumps 45, 54 or flow of air or liquid to the heat exchangers32, reservoirs with heat exchange capability 34 or reservoirs with heatexchange and separation capabilities 35. Therefore, the pressure in thechambers can be controlled to optimize the PV and corresponding leakrate for the affected seals 17, 28 a, 28 b, 28 c or 27. It is alsopossible to use a control system for temperature monitoring of thelubricant 29 at the high pressure chambers 39 and low pressure chambers26 a, and 26 b, or in the high pressure lubricant circulation system 30and low pressure lubricant circulation system 31 such that the controlsystem monitors temperature, pressure and flow to determine if processfluid 56 has condensed or become miscible in the lubricant 29, or if theprocess fluid 56 has remained in vapor state. Temperature monitoring maybe used in addition to or as an alternate to pressure monitoring, shouldthat be required.

Combinations and Configurations of the Concepts

One such combination, not shown for the purposes of brevity, isutilization of splash lubrication of the bearings, gears and seals inthe high pressure chamber 39, pressure balancing chamber 39 with processfluid 56 pressure from process pipe 60. In the pressure balancing lineswould be a separator 77 to insure that lubricant did not make it intothe process. The low pressure end of the machine 21 would have alubricant circulation system 31 with pressure balancing of chamber 26 awith process fluid pressure from process pipe 70. Similar to the highpressure side, the low pressure side would utilize a separator 77 in thepressure balancing line 72. The lubricant circulation system 31 would becontrolled by the control module 93 and it would be tied into theseparator 77 with a vent line off of the reservoir with heat exchangeand separation capabilities 35 that would alter the temperature of thelubricant to keep it in the desired range.

Additionally, it should be understood by those skilled in the art thathigh pressure process pipe 60 and low pressure process pipe 70 may beadvantageously coupled in various configurations to any of the highpressure chamber and one or more low pressure chambers (with or withoutan integrated gear box). The couplings may be accomplished using any ofthe techniques described above, including one or more regulators and/orpressure balancing lines to achieve cascading and pressure balancing,depending on the application needed.

Furthermore, it should be noted that specific lubricants, described invarious embodiments above, may have advantageous effects on theoperation of the disclosed systems/machines. As is known in the art, alubricant's purpose is to keep moving parts separated from running metalon metal. Properties of the lubricant affect its operating temperature,viscosity, and so forth. It has been found by the Applicant thatsynthetic lubricants may be advantageous if using a hydrocarbon processfluid in pressure balancing. For such applications, suitable syntheticlubricants include poly-alpha-olefin (PAO), polyalkylene glycols (PAG)and the like. These synthetic lubricants have advantages over mineralbased lubricants for very low or high temperatures, extremely highloads, extraordinary ambient conditions, and flammability. Exemplaryphysical property advantages include thermal resistance, low temperatureproperties (fluidity, pour point), flash point and evaporation losses

Further advantages of synthetic lubricants (depending on the basematerial) over mineral lubricants include improved thermal and oxidationresistance, higher viscosity index, improved low temperature properties,lower evaporation losses, reduced flammability, better lubricity, andlower tendency to form residues. Accordingly, for use in a pressurebalanced system that uses a hydrocarbon based process fluid, minerallubricants are not particularly suitable due to the risk of solubilityand miscibility issues. Hydrocarbon based process fluid (in this case,isobutane) near saturation conditions would be contacting the lubricantand that liquefied hydrocarbon could mix with the mineral basedlubricant. Accordingly, a number of resulting effects occur, where (i)dilution with isobutane will drop the viscosity of the oil, (ii) thelubricity of the oil is most significantly affected by its viscosity,(iii) there is uncertainty to what extent the mixing will occur, and(iv) the lubricant properties will return to their original state whenthe process fluid is boiled out of solution, but if that is noteffectively accomplished, the risks are very high to damage to therotating components due to the mineral based lubricant not performing asdesigned. Also, most lubricant circulation systems look to cool thelubricant. In the systems presented, it may be necessary to heatlubricant (to boil off any process fluid in the lubricant), therefore asynthetic is better suited to operate at higher temperatures thanmineral based lubricants.

Specifically, many mineral based lubricants operate at temperaturesbelow 200° F. whereas a synthetic PAG is suitable to operate up to 200°C. As an example, to evaporate isobutane at the lubricant circulationsystems operating pressure of 180 psi, the lubricant must be over 170°F.—near the upper limit to mineral based lubricants. The “rule-of-thumb”is that for every 10° F. that a mineral based lubricant is over 180° F.,it useable life expectancy is reduced to half. The reason for this isthat as lubricants rise in temperature their viscosity goes down andtherefore the lubricity of the lubricant is affected and it breaks downquicker. With the higher suitable operating temperatures of syntheticlubricants, the designs presented can operate the lubricant at anelevated temperature and not lose the lubricating properties requiredfor the bearings and other moving parts. Synthetics also have a higherviscosity index and therefore are better suited for machines thatoperate outdoors, in the field. That is, if a cold start, in winter, isrequired, a high viscosity index lubricant will have a cold temperatureviscosity closer to that at elevated temperature viscosity, making thelubricant circulation system easier to operate.

Accordingly, regarding lubricant circulation systems for the variousconfigurations of the present disclosure, the configurations may bebased on splash or circulating lubrication. In the case of circulatinglubrication, the configuration may be single system for entire machineor a lubricant circulation system for each pressurized chamber, or acombination of any of the three types of systems on one machine. (e.g.splash lubrication on the high pressure chamber end, with two lubricantcirculation systems for each pressure chamber 26 a and 26 b.) or, splashon the high pressure end with one lubricant circulation system for twopressure chambers, where the lubricant is pushed from the higherpressure chamber to the lower pressure chamber by the pressure. Aregulator in the lubricant line connecting the two chambers would berequired. This is where the lubricant circulation system configurationand the pressure cascade will allow the lubricant to be circulated withone system pump. Due to the risk of viscosity being too high to pump incold starts, and lack of certainty that the lubricant will be deliveredto the various elements when the viscosity is considerably higher thanthe designed system, it may pose too risky to rely on a system with asingle circulating pump.

In the foregoing Detailed Description, it can be seen that variousfeatures are grouped together in individual embodiments for the purposeof streamlining the disclosure. This method of disclosure is not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter lies in lessthan all features of a single disclosed embodiment. Thus the followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separate embodiment.

What is claimed is:
 1. A system for balancing pressure or reducingpressure differential across seals, comprising: a machine, configured tohandle process fluid, the machine comprising a higher pressure processpipe and a lower pressure process pipe; a first pressure chamber,operatively coupled to one portion of the machine, wherein the firstpressure chamber is configured to be pressurized by the process fluid,the first pressure chamber comprising a first chamber seal; and a secondpressure chamber, operatively coupled to another portion of the machine,wherein the second pressure chamber is configured to be pressurized bythe process fluid, the second pressure chamber comprising a plurality ofsecond chamber seals; wherein the machine is configured to provideprocess fluid to at least one of the first pressure chamber and secondpressure chamber to reduce the pressure differential in one of (i) thefirst chamber and the second chamber, and (ii) a volume between each ofthe plurality of second chamber seals.
 2. The system of claim 1, furthercomprising at least one first pressure balancing line coupled to thehigh pressure process pipe, wherein the first pressure balancing line iscoupled to at least one of the first pressure chamber and secondpressure chamber, and operative to assist in the reduction of pressuredifferential across the seals.
 3. The system of claim 2, furthercomprising at least one second pressure balancing line coupled to thelow pressure process pipe, wherein the second pressure balancing line iscoupled to at least one of the first pressure chamber and secondpressure chamber, and operative to assist in the balancing of pressureacross the seals.
 4. The system of claim 1, further comprising one of:(i) at least one first pressure balancing line comprising at least onepressure regulator coupled to the higher pressure process pipe, whereinthe first pressure balancing line is coupled to at least one of thefirst pressure chamber and second pressure chamber, and operative toassist in the balancing or reduction of pressure differential betweenthe process and pressure chamber, or between one pressure chamber andanother pressure chamber, or (ii) at least one second pressure balancingline comprising at least one pressure regulator coupled to the lowerpressure process pipe, wherein the second pressure balancing line iscoupled to at least one of the first pressure chamber and secondpressure chamber or subsequent cascading pressure chamber, and operativeto assist in the balancing or reduction of differential pressure.
 5. Thesystem of claim 1, wherein the machine is configured to cause at least aportion of process fluid during the reduction of pressure differentialto flow into the first pressure chamber.
 6. The system of claim 5,wherein at least one of the first pressure chamber and second pressurechamber is configured to contain lubricant.
 7. The system of claim 6,further comprising a separator configured to: (i) receive the processfluid from the first pressure chamber and remove at least a portion ofthe lubricant, or (ii) receive the process fluid from the secondpressure chamber and remove at least a portion of the lubricant.
 8. Thesystem of claim 1, wherein the machine is configured to cause at least aportion of the process fluid during the reduction of pressuredifferential to flow into the second pressure chamber.
 9. The system ofclaim 8, further comprising a separator configured to receive theprocess fluid from the second pressure chamber and remove at least aportion of the lubricant.
 10. The system of claim 1, wherein the secondpressure chamber comprises a gear mechanism comprising a drive shaft, anoutput shaft and an integrated gear mechanism, wherein the plurality ofsecond chamber seals are configured to seal the second pressure chamber.11. The system of claim 1, wherein the system is configured to reducethe pressure differential by adjusting a pressure differential betweenat least one of (i) the first chamber and the process, (ii) the secondchamber and the process, (iii) one of the plurality of the secondchamber seals and the process, and (iv) one of the plurality of thesecond chamber seals and atmosphere.
 12. The system of claim 1, whereinthe machine is configured to provide process fluid to alter first orsecond chamber pressure to reduce the product of a pressure differentialand surface velocity (PV) of any of the seals in the machine.
 13. Amethod for balancing pressure, comprising: providing process fluid in amachine, the machine comprising a higher pressure process pipe and alower pressure process pipe; pressurizing, via the process fluid, afirst pressure chamber operatively coupled to one portion of themachine, wherein the first pressure chamber comprises first chamberseal; pressurizing, via the process fluid, a second pressure chamber,operatively coupled to another portion of the machine, wherein thesecond pressure chamber comprises a plurality of second chamber seals;and providing process fluid to at least one of the first pressurechamber and second pressure chamber to reduce the pressure differentialacross the seals in one of (i) the first chamber and the second chamber,and (ii) a volume between each of the plurality of second chamber seals.14. The method of claim 13, comprising the step of altering chamberpressure via at least one first pressure balancing line coupled to thehigher pressure process pipe, wherein the first pressure balancing lineis coupled to at least one of the first pressure chamber and secondpressure chamber, and operative to assist in the reduction of pressuredifferential across any of the seals.
 15. The method of claim 14,comprising the step of altering chamber pressure via at least one secondpressure balancing line coupled to the lower pressure process pipe,wherein the second pressure balancing line is coupled to at least one ofthe first pressure chamber and second pressure chamber, and operative toassist in the reduction of pressure differential across any of theseals.
 16. The method of claim 13, wherein at least one of the firstpressure chamber and second pressure chamber is configured to containlubricant.
 17. The method of claim 16, further comprising a receiving anamount of process fluid from the first pressure chamber in a separatorand removing at least a portion of the lubricant from that processfluid.
 18. The method of claim 16, further comprising receiving anamount of process fluid from the second pressure chamber into aseparator and removing at least a portion of the lubricant from thatprocess fluid.
 19. The method of claim 13, wherein the second pressurechamber comprises a gear mechanism comprising a drive shaft, an outputshaft and an integrated gear mechanism, wherein the plurality of secondchamber seals are configured to seal the second pressure chamber. 20.The method of claim 13, wherein providing process fluid to at least oneof the first pressure chamber and second pressure chamber to reduce thedifferential pressure comprises adjusting pressure between at least oneof (i) the first chamber and a process side, (ii) the second chamber anda process side, (iii) one of the plurality of the second chamber sealsand a process side, and (iv) one of the plurality of the second chamberseals and atmosphere.
 21. The method of claim 13, wherein providingprocess fluid comprises altering first or second chamber pressure toreduce the product of a pressure differential and surface velocity (PV)of any of the seals in the machine.